Buy a Secuyou Smart Lock and download the app for free, so you can control your patio door automatically with your smart phone. Secuyou Smart Lock has a 5 digit code that you can share if you want to allow others to unlock and unlock with a smart phone.
Secuyou Smart Lock is controlled via Bluetooth Smart (trademark of the Bluetooth SIG). Locks automatically locks when the Bluetooth connection is disconnected.
And when the smart phone restores the Bluetooth connection, you can unlock using the button on the Secuyou Smart Lock.