There’s been a flood of smartphone controlled deadbolts, like Lockitron, of late, especially from Kickstarter. Now comes the natural progression to padlocks from FUZ Designs called Noke (pronounced No-Key) for $80 on Kickstarter. Just like the deadbolts, this padlock is controlled by your smartphone via Bluetooth, freeing you from having to carry a key or a 3 digit combination in your brain.
Take a look at this video that explains the features. Yes, they explain what happens if you don’t have your smartphone with you.
In the not distant future, you will only need to carry your smartphone to do anything.