I didn't watch the video you're referring to, but I imagine one way that this could work would require sharing your private key with a third party. The third party would periodically check the blockchain for a lack activity from the address. If some threshold of dormancy is reached, it would use your keys to send to some predefined address.
There are a few use cases where such a system could prove benficial.
- Estate purposes; bitcoin inheritance
- Recovery from catastrophic data loss (simultaneous failure of digital media and all forms of backup)
- Fund locking
Once the timining mechanism is in place, there are some other potential uses that wouldn't necessarily have to be triggered by inactivity. Think about maybe annuities or trust funds... though, ideally, if you are setting it up for these purposes then you may not wish for the BTC to just sit idle. Right now that seems to be a good idea, considering the infancy of the currency and it's rapid valuation, but eventually this may taper off and one would want a different method of investment (perhaps MPEx type of funds will mature a bit with bitcoin, or some interesting form of bitcoin banking will develop further).
Still, these are just a few ideas and speculation..
