[frossie]

So, this is a good idea, but won't replace actual postcards for me

Well I have been doing this with the Postino iOS app for a couple of years now and it has replaced postcards for me (though obviously I don't expect it to do so for everyone).

The two killer features for Postino are (a) the convenience, for example you don't have to obtain stamps or find a postbox and (b) KIDS. Your parents are probably a lot more likely to want a picture of their grandkid in front of the Eiffel tower, rather than just the Eiffel tower itself.

I agree about the message being equally important though, the Postino app allows for a non-trivial amount of text and a hand-drawn "signature".