Camra did have an app but due to some changes on Android it started to malfunction and so was withdrawn from the Google app store. I think its still around for apple.
www.whatpub.com works well, more so if you are a Camra member because you can turn the adverts off and score the beer. It doesn't tell you what beer is on in real time but gives info on what the staple beers are for a particular pub.
Camra vouchers are accepted in a lot more pubs than just Wetherspoons. I always forget to carry mine.