アプリのversion等を取得する方法

MLで聞いたら教えてもらえました。ありがたや。。

http://groups.google.com/group/google-appengine-java/browse_thread/thread/e6bfcbfafd4f6e1e

You can try using ApiProxy:
import com.google.apphosting.api.ApiProxy;
...
String version = ApiProxy.getCurrentEnvironment().getVersionId();

Note that this isn't an official method and this API may change without
warning in later releases of the SDK and production environments, so you're
definitely not encouraged to rely on it for your production apps. Still, it
should work, at least for now. 

非公式なので非推奨だけと、とりあえず使えるそうです。