yes they exist, and yes, it is worth it! My first sponsor started online, graduated to phone contact too. Not sure if it's ideal, but it's a heck of a lot better than going without.
I now live in an area with no meetings, so my sponsor is mostly phone contact from 2000 miles away. We've met F2F three times.
The main thing is to remain honest and willing. It's easier to hide from an online or long distance sponsor, to lie about what's going on. But like I said, it's much better than going without.