There is the old maxim (earliest source I can find here):
All bicycles weigh fifty pounds. A thirty-pound bicycle needs a twenty-pound lock. A forty-pound bicycle needs a ten-pound lock. A fifty-pound bicycle doesn’t need a lock.
The Skylock breaks that rule and a whole pile of others. It costs as as much as a bike (US$159 pre-order, US$249 retail) but does a lot more than your usual U-lock. Through bluetooth or Wifi, you are always connected to your lock with your phone; the lock will call you if someone tries to steal the bike.
Skylock is equipped with a triaxial accelerometer to detect tampering conditions. If a potential tamper condition exists, the lock will send an alert to our cloud servers which I turn will let the owner know, (if the bike is in a wifi zone or within Bluetooth range. Otherwise, it is a dumb but strong lock)
You open it with your phone, either with a swipe or you can set it up to unlock automatically by proximity. If you hit something, it will ask you if you are OK and if you don't give the right answer, it will call for help. You can even set up an informal bike share system using the app to send permission to another smart phone.
It will run for a month on a full charge, but keeps itself topped up with a small solar panel. If you lose your phone or it runs out of juice, you can always punch in a combination. If the lock runs out of juice, you can jump-start it with a phone charger. These guys (former Boeing and Jawbone engineers) seem to have thought of everything.
The always hilarious Bike Snob NYC is not impressed, thinking it all overly complex, but I am; I always misplace my keys but am glued to my phone. Everything is getting connected in the Internet of things, the Mesh City, and having my lock talk to my phone seems like one of the better ideas.