As much as the Bible tells us about the afterlife, there are many questions we might ask that it either doesn't give a satisfactory answer to, or doesn't address at all. Chief among these questions is exactly how much can those who are currently dead see, or interact with, we who are still alive?
Ultimately, although the Bible does give us plenty of information to work with, it never directly says whether or not they can see us. We do know that Paul, being absent from the body, is now present with the Lord (2 Corinthians 5:6-8; Philippians 1:23), but what is he doing there? We see in Revelation 6:10 that the martyrs of the tribulation call upon God to expedite justice for them, but can they actually see the Earth, or are they just asking God to punish their persecutors? And of course, the reason we ask all of this is because we want to know, can I talk to grandma?
To begin with, I want to express my personal view and why I hold it. I lean towards no, but with exceptions. My weakest argument (keep the word "weakest" in mind there) is that they can't see us for the same reason we can't see them. Our "location" is different. Of course, I use air quotes there in anticipation of the most obvious push-back: It's not a matter of location, but state. We can't see God, though He is omnipresent, but He can see us. But I'm not willing to speculate about what abilities the dead might have beyond our own. What would even be required for them to see us, I don't know, and unless you find it written in Scripture, neither do you.
But of course, there are exceptions. The Transfiguration, for example. When Moses and Elijah appeared on the mount with Christ, I assume they were able to see more than just Jesus' face on an otherwise blank background. Peter, James, and John, were there, so Moses and Elijah could probably see them. Similarly, when Saul called up Samuel via the witch at En Dor, Samuel and Saul spoke to each other, so obviously Samuel could perceive Saul. However, I believe these are exceptions.
In the case of Samuel, even his reaction suggests if he could see the Earth, he wasn't paying it much attention. "Why have you disturbed me by bringing me up?", he asks (1 Samuel 28:15). Does this mean he couldn't see the Earth? Maybe floating around looking over his relatives? Explicitly, no. He could have just been annoyed that Saul, having rejected the counsel of God Himself, tried to circumvent God by calling Samuel up. But it seems more likely that Samuel was more preoccupied with his own, spiritual life, than the things of the Earth of which he was no longer a part.
Of course, ultimately, what Saul did was a flat out sin, because the Old Testament forbids necromancy. God not only forbade the practice of communicating with the dead, but commanded the death penalty for it (Exodus 22:18; Leviticus 19:31; 20:6, 27; Deuteronomy 18:11), and even told us that the former inhabitants of Israel were being cast out of the land for this very practice (Leviticus 18:24-29).
Using this as a foundation, Isaiah declares "And when they say to you, “Seek those who are mediums and wizards, who whisper and mutter,” should not a people seek their God? Should they seek the dead on behalf of the living? To the law and to the testimony! If they do not speak according to this word, it is because there is no light in them." (Isaiah 8:19-20). There is no light in those who do not speak according to the word "to the law and to the testimony", specifically regarding those who seek out the dead. One thing that is clear, then, is that regardless of whether or not they can see us, we, as Christians, should not be seeking them until we join them.
One probable extension of this is that they cannot see us, either. It is not a necessary conclusion. After all, it is equally immoral to ask the devil for help, but if you don't think he has direct access to you, you're easy prey for him. But it seems unlikely that God, who has explicitly commanded us not to seek the dead, would then allow the dead to seek us. After all, He does not tempt anyone (James 1:13-14).
This leads us to the ultimate division of the dead. We all know where we want the dead to go. "They're in a better place", we say. "Rest in peace", we write on their grave markers. And for the saved, this is true. When those who are in Christ die, they go to be with Him, a far better place in which we receive a very peaceful rest. But for the impenitent, eternity is bleak. They are restrained, waiting in agony for the time they will be cast into the second death (Revelation 20:14).
In Luke 16:19-31, we get a glimpse into this realm: "“There was a certain rich man who was clothed in purple and fine linen and fared sumptuously every day. But there was a certain beggar named Lazarus, full of sores, who was laid at his gate, desiring to be fed with the crumbs which fell from the rich man’s table. Moreover the dogs came and licked his sores. So it was that the beggar died, and was carried by the angels to Abraham’s bosom. The rich man also died and was buried. And being in torments in Hades, he lifted up his eyes and saw Abraham afar off, and Lazarus in his bosom. “Then he cried and said, ‘Father Abraham, have mercy on me, and send Lazarus that he may dip the tip of his finger in water and cool my tongue; for I am tormented in this flame.’ But Abraham said, ‘Son, remember that in your lifetime you received your good things, and likewise Lazarus evil things; but now he is comforted and you are tormented. And besides all this, between us and you there is a great gulf fixed, so that those who want to pass from here to you cannot, nor can those from there pass to us.’ “Then he said, ‘I beg you therefore, father, that you would send him to my father’s house, for I have five brothers, that he may testify to them, lest they also come to this place of torment.’ Abraham said to him, ‘They have Moses and the prophets; let them hear them.’ And he said, ‘No, father Abraham; but if one goes to them from the dead, they will repent.’ But he said to him, ‘If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead.’ ”"
Now, right away, we see that it is impossible for the dead to cross into each other's realms, so it seems odd that they might be able to pass into ours. Certainly, it seems unlikely that the rich man can, as he certainly wants to. "Send Lazarus", he says, as he suffers in torment. Yet the thought doesn't cross his mind that he can leave, only that Lazarus can.
We see, then, that those in Hades cannot pass from their realm to ours, and those in Paradise, assuming they can, won't. But we're missing the key point here. Although everyone involved does have some self-interest (the rich man focusing on his agony, Lazarus enjoying his reward), everyone has a higher focus: Eternity.
The rich man, not wanting his brothers to share his fate, wants Lazarus to visit them and tell them to repent. This is the will of God. He commands all men, everywhere, to repent (Acts 17:30). And those who do, those who diligently seek Him, will receive rewards, like Lazarus. But of course, Abraham tells him he's still missed the point. Lazarus going to them won't change their hearts. They must hear Moses and the prophets.
The dead, then, seek the will of God. If they could speak to us, their message would be repent. They would rebuke us for seeking them over God, and point us to Him. They certainly do not, as some denominations teach, intercede for us with Him, for there is one God, and one mediator between man and God: Jesus Christ (1 Timothy 2:5).
With all of this in mind, we actually have to ask, regardless of whether or not they can see us, do we even want them to? Especially in our worst times. Do we want grandma to see us cussing out our mothers? Do we want grandpa to watch us fornicate? Keeping in mind, having been purified, they are more Holy than we are: Do we want the dead to watch in horror as we seek them over God?
With all of this in mind, the question "can they see us?" isn't easy to answer. But it turns out to be the wrong question. It makes sense that we would want to continue fellowship with those we miss. And indeed, we should miss them. It's sad when people pass from this realm to the next. The Bible even calls death an enemy. But none of this should distract us from the pursuit of the Living God, and ultimately, He commands us to let the dead sleep where they lie. Our eyes should be on Him, just as theirs are.