In article >, Paul Hovnanian P.E. wrote:

> Has anyone looked into building a sniffer for these r.f. signals? One
> wouldn't need to decrypt the content, only detect its presence (although
> one system that broadcasts GPS car locations might be interesting). Then
> you'd have an alarm for law enforcement in the vicinity, even if they
> were just pacing people or using a stopwatch.

Time to write up your patent application!