Steve, check out the Valentine 1. I have one and having the ability see where the alert is coming from cannot be overstated. You also mentioned a cordless type strapped to your rollbar, all I can say about that is everytime an independant does a test of the cordless units they get pounded. You may want to look into the remote mount option for the V1. All the coverage but with stealth.
http://www.valentine1.com/