Is there a system superior to the FLARM-type system, which A) does not require a power source other than battery, B) costs as little as the FLARM and C) is always effective in alerting to nearby traffic?
FLARM has low power consumption because it transmits at low power and is therefore low range. It costs less than a transponder because it does not meet a certified standard. If you mandate FLARM, and therefore require certification, and increase its power to something more generally useful, you end up with something that is as expensive and power hungry as Mode S.
What we need is a low power, uncertified system that works over 1090ES and is therefore compatible with the vast installed base of Mode S and TCAS.