Technology used in LED stumps and bails in WorldCup-2015?
I found a Cricket Australia article that says &quot;The ICC approved the use of the zing bails for international cricket in July 2013&quot;. Zings International is a company based in Port Adelaide, Australia and it appears the system was intvented by one of their directors Bronte Eckermann. Doing a patent search on his name the following appears to be the relevant patent:
System for indicating movement of an article from one position or orientation to another position or orientation that contains the following drawings that is probably the most interesting one:

The patent leaves open a fair few possibilities for different technologies but the preferred embodiment and the one shown above is based on measuring inductance. The parts maked 44 and 48 are inductors and from the patent:

With the inductors 44 and 48 in the circuit as shown, the LED's have higher resistance than the inductor coils which have much lower resistance. When the circuit is initially powered the LED's glow. When the circuit is opened, the lights shine very brightly and then quickly go out. This is due to the inductors initially providing a high resistance until a magnetic field is built up at which time the inductors provide less resistance taking current away from the lights which travels through the inductors which by now are low resistance.
When current first starts flowing in the inductor coils, the coils build up a magnetic field. While the magnetic field is building, the coils inhibit the flow of current. Once the magnetic field is built up, current can flow normally through the wire. This is typical inductor operation. The present invention employs an inductive loop including an inductive sensor to detect any change of inductance. When a change of inductance is detected, the LED light triggers.
Each bail has an inductive loop in each arm. A metal pellet in each bail when the bail moves causes a change in inductance, triggering the indicating light. When the stump is placed under the inductive loops in the bails, the bail senses the inductance and monitors the inductance regularly. When the metal saddle in the stump is moved away from the inductive loops, such as by removal of the bails, the bail senses a change in inductance and the LEDs flash for a few seconds and then preferably turn off to save power.

The patent is a relatively recent one filed in 2010 and no doubt some improvements have been made, for example the above seems based on a simple analog circuit whereas their web page describes the bails as having a microprocessor. So it's hard to know exactly what technology they currently use but that system seems to have been the initial method for the bails. The patent doesn't seem to include details on the operation of the stumps and I couldn't find any related patents.