Did I not read something in a magazine recently that NATS had taken up the challenge of electronic conspicuity for light aircraft? Following the success of their other projects they were looking at a light weight low power/cost ADS-B based product.
Ah ha! found some of it in December 2011's iAOPA
In the UK, NATS is attempting to drive R&D on the issue. But the level of European or government funding is almost non-existent, again in stark contrast to the USA. In some cases, we need to actually disable the function in our US-specified box when flying in Europe!