I keep thinking about building something like this but the thing that ours me off is the possible implications in the case of having to claim on insurance if someone robbed my house.
I have very little doubt that the insurance company would take a dim view of my front door lock being connected to the web, and leap on the chance to deny any claims on the grounds that the intruder could have broken in via my code, making it equivalent to leaving the door unlocked when going out.
Honestly, you sound unnecessarily paranoid about this. There are tons of mainstream remote-controllable locks these days. Walk down the door hardware aisle of HD or Lowe's and you'll see multiple options from Kwikset, Schlage, and some off brands as well.
Your insurance does essentially protect you from yourself. As long as you don't do anything that intentionally makes your house more attractive to burglars (like a neon sign in the window indicating door lock status) the likelihood of what you describe (a claim denial) is nil.
This assumes that the intruder was able to get into the house without breaking something, which I would assume occurs rarely... unless you actually do leave the door unlocked.
I have very little doubt that the insurance company would take a dim view of my front door lock being connected to the web, and leap on the chance to deny any claims on the grounds that the intruder could have broken in via my code, making it equivalent to leaving the door unlocked when going out.