... If someone gets access to your Coinomi wallet it's obvious that he/she will have access to your private keys without any difficulties too. You should use Biometric security to protect your phone so that no one can access it but only yourself....
Never ever ever rely on biometic security. There have been many vulnerabilities found over the years. And more keep popping up. A long c0MpL3x password is the only way to go. Now, also if you never keep more then $50 in your phone wallet, then you probably care less then if you keep $5000 It's a matter of time and effort vs. security vs. possible loss.