It is difficult to know definitively just what it is that our loved ones know and observe if they are in heaven. Scripture makes it clear that those in heaven rejoice when even one sinner repents, and we know from scripture that the martyrs beneath the altar(described in the Book of Rev) cry out to God asking when He will avenge their blood. Obviously, they are aware of what is going on with those still on earth.
Whether or not our loved ones are allowed to give us signs is not really known to us. Such a privilege is certainly possible and has no doubt happened, but this may not be the norm. Everything is according to the wisdom, mercy, and love of God. We need to be careful about interpreting something as a sign from a loved one in heaven. I personally know of some cases where it is extremely difficult to interpret certain signs in any other way.
I do believe that those in heaven watch over us and pray for us. In Hebrews 12:1 we are told that:
“…we are surrounded by so great a cloud of witnesses, let us also lay aside every weight, and sin which clings so closely, and let us run with perseverance the race that is set before us,”
Paul tells us in Romans 8:38-39 that:
“For I am sure that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord.”
As the body of Christ we cannot be separated. Even when we die we remain part of the body of Christ. Those in heaven are that cloud of witnesses that are part of the body of Christ. They do care about us and watch over us in love and in prayer.
I hope this helps.