At the ripe old age of 80 there are probably very few things Dad hasn't received as a gift at some point in his lifetime. After a certain age birthdays and holidays become less about the gift getting and more about simple things, like spending time with your family. Give your father the gift of love and memories of a long, fruitful life.
By the time you get to 80 you must likely have all your basic necessities and may not want to learn to use newer technology. Instead of giving your dad an object, consider spending time with him. Offer to drive him to the store or accompany him on a fun trip. Take the grandkids over and have a family party suited to his taste with his favourite food, people and music. Make up "coupons" like children do that say things like "good for an afternoon of flying kites" or "good for a weekend of hunting." Create a photo album of him with people he loves and give it to him to look at when he is lonely. If he has dementia, an album with notes alongside the pictures may even help him remember people better.
Many older people can be too proud to ask for help when they need it. Instead of saying "Hey, Dad, do you need money for medicine?" simply drop by with some groceries or pay off this month's mortgage. He may or may not thank you for it but it will give him the chance to do something out of the ordinary or to buy something normally out of his price range without offending him. You can also buy a refillable gift card or shopping card for a store he enjoys and add more money to the account regularly so that he can buy his necessities independently. You could also buy a long-distance calling plan for him to keep in touch with family and friends.
Find out what your father's favourite things were when he was younger. If possible give him things like a CD version of an old record he once loved that broke, so he can listen to it again. Or make a basket of treats like candy and pastries he might have loved when he was younger (in sugar-free versions if necessary). A collection of books by a favourite author, a comfortable chair or new bed, or gift tokens to restaurants, if he is a foodie, all make wonderful gifts. If he can travel, you may also want to give him the trip of a lifetime. Find out that one place he has always wanted to go to and take him there.