Android applications security risk

Is there any way to sign out of the Android application? We’re wanting to use it to track highly sensitive patient level data in the field but can’t find a sign out option in the application. I’m concerned that if a field worker loses a phone this is a serious security risk. Am I missing something, or is there no way to sign out of the application without wiping the local data? Is this a feature still planned for future?

Regards

Ed