Are we reinventing the wheel here? This is not the first requirement for this type of device. Witness remote access door entry locks in apartment buildings. I found **broken link removed** and **broken link removed** by doing a Google search for "electric door latch". I'm pretty sure they're the same part, but there are probably others that would work if this doesn't fill the need. I just wonder how this one handles power outages. If it had a key for outside access and a knob for inside access (which seem to be required in any case), that would solve the problem.
The problem with a simple solenoid is that it doesn't allow the door to fully close and latch once it has been opened unless you actuate it again. Otherwise, the door will close against the extended solenoid bolt. QEMA's latching circuit solves that problem, but it requires a conscious effort to relock the door, which doesn't seem reasonable.
Basically, what is required is a bolt which retracts automatically when it hits the strike upon closing (like an ordinary latch), but can only be opened by a key from the outside and a knob from the inside.