The usefullness an success of devices like FLARM require a broad diffusion of compatible devices
Just to check, your FLARM thing will only work against other FLARM equipped aircraft? And what % of GA aircraft are so equipped, in say, the UK?
Obviously if it works, and it gets over say 50% of aircraft equipped... it becomes useful and worth having. But there's rather a chicken and egg before that?
Gliders I'd rather leave out of it - they are somewhat unique in "congregating" in areas risking collisions, and a close community where establishing the critical mass may work (or already has?).