To access the latest versions of Rocket Player or iSyncr, we need to join the Google+ community (either Rocket Player or iSyncr). Once you've successfully followed the tutorial and joined the beta, an update for the app will be available on Google Play.

Rocket Player community
iSyncr community

To join the community open Google+ on your Android device.

Search for Rocket Player/iSyncr and select "Join community".

Select "Become a tester".

Wait for up to 24 hours, then look for an update to Rocket Player or iSyncr on Google Play.