doorbot is described as 'Uses a raspberrypi and a solid-state relay to unlock the door. A node server running optionally elsewhere manages the users and serves the WebUI. (no affiliation to Ring which used to be called doorbot)'. There are five alternatives to doorbot for iPhone, Android and Online / Web-based. The best alternative is Nold, which is free. Other great apps like doorbot are Kisi (Free), Kevo (Free), Sesame (Paid) and Lockitron (Free).
Nold offers a smartphone based access control system for both personal and business use. Using your phone as a key, you can open garage doors, entry gates, office doors and more. The system can manage all guests and keys remotely in the cloud.
Kevo – Your Phone Is Now Your Key Download the Kevo app for use with the Kevo Smart Lock made by Kwikset and Weiser. With Kevo, your Smartphone is now your key. No more fumbling for your keys. Keep your phone in your pocket or purse and just touch the lock to open.
Sesame allows users to lock and unlock their doors using the Sesame app on their smartphones. It is the only smart lock that syncs the movement of the lock with the phone, providing exact control of the angle to which the lock turns.