I thought you expats might have some good suggestions here...
All of mine and DHs siblings live abroad, longhaul flights and unlikely to return. We've just become an aunt and uncle for the first time and it's hit us a little that it's going to need more effort to remain close.
They're in China so no Facebook, gmail etc. Nothing sent by post from any of us in the UK has ever reached them at home, we can sometimes get cards delivered to their work addresses but wary of ever sending anything of value.
We have the apps for their facebook/whatspp alternative and have family group chats and can video call through this, time zones and busy lives permitting.
We will be visiting them next year but it's unlikely to ever be frequent meet ups unless we never take any other holidays due to the distance, costs, visas etc.
Is there anything else I'm missing? I guess I'm a little sad I've missed newborn snuggles and will never be able to pop a card in the post or drop a Christmas present round. I still want to be a good Aunt!