For my android app development, I am trying to get logcat messages from my real device (when starting an app on it from eclipse) and not just from my emulator.
It works like the emulator, use the ddms or eclipse plugin to get the logcat from your app running on devices.
Otherwise you have always the options to use a Log Collector app (download a free one from Market), you can tell your users to use such app if they want to send you the log.