Today’s invention is a new way to foil would-be pickpockets (see this for an illustration of how insecure your portable possessions actually are).
Many of the nefarious techniques employed to steal stuff involve distracting the owner, so that he or she fails to notice the theft.
Now that we have ubiquitous touchscreens, why not use these to protect our valuables?
Imagine a smartphone with a slim case in which other items such a credit card and some notes could be carried on the back (blue).
The phone would require that it be held in a particular finger configuration (red) as it was being extracted by the owner from his pocket (one of say 100 such patterns).
If the device detected the acceleration associated with such extraction, whilst the screen was gripped in the wrong way, it would automatically ring and issue audible alerts.
It might also tweet and message your friends in order to alert any travelling companions.