I've also got a 50D and, rather dimly, bought the App without checking the list of supported cameras. When I tried it, it didn't work. Surprise surprise. Finding the 50D wasn't supported, I contacted the app website, Dire Studio, and asked if they had any plans to support the 50D retrospectively. Apparently they have but need some beta testing. I'm going to have a go at helping out. I'm sure they would be glad to hear from other 50D owners who'd also like to help.
Glad to hear there's a few other 50D users wanting support. I know a few people that would like it too. I'll shoot them an email so they know there's more interest.