My children live over 1000 miles away from their grandparents. But not one day goes by without them asking to speak to them. Having a good relationship with your grandkids will help you stay connected with them even when you cannot visit them in person. It is simple, kids enjoy your time and company. Both which you can provide them with over the phone! My children are two and five. They love to play pretend. When my mom calls over facetime, she gets their attention by acting like a kid! She plays dress up with them, has a tea party, tells them stories, encourages them to play games like "rowing a boat" using a card board box and many more cool things. It is all about how creative you can get with the kids.
For older children you can send books, care packages, encourage talks about politics, religion and other world issues. Even older kids are curious and sometimes they like to get a different perspective!
Take a chance, pick up the phone and talk to your grandchildren! Chances are, they will end up surprising you.