This is a dreadful event which any pilot would want to avoid.
However, the solution for GA is not as simple as putting a gadget on the panel
to do the looking for us.
The FLARM is a good device for glider pilots in the environment they fly. But only any good if all the other aircraft likely to be met in the air are likewise equippped.
I have installed a FLARM system to a GA aircraft engaged in glider towing. When fitted to a powered aircraft it needs to be heard over the noise of the engine and radio. It will therefore need to be properly powered and connected to the aircraft's audio system. This will involve a modification to the aircraft which will need CAA approval (for a fee) and installation (for a fee).
To connect the FLARM to the audio you will also need a FLOICE unit, which is a voice-intercom interface.
Remember that a glider pilot usually has a bubble canopy with excellent vision capabilities so in the event that a FLARM warning is given (visible and audible) the pilot can quickly look for the conflict and take avoiding action. I believe the range of the FLARM is such that a warning is given 15-20 seconds before possible conflict.
Most GA aircraft do not have such good all-round vision and as such, a FLARM alert may not give the pilot time to digest the audible and visible information, look out to verify, given the many blind spots inherent in GA aircraft and take the correct avoiding action.
As is so often the case in these events, it is better to wait for the AAIB report before deciding a course of action based on where the perceived problem was in this case.