HomePatrol makes sense to me for RV'ing. It uses the Radio Reference database to obtain frequencies for local areas which are defined by zip code or determined by interfacing the scanner with a GPS. Trunked systems and digital systems are automatically programmed by the radio and database. The updated database is downloaded via the internet and uploaded into the scanner by USB cable.
For more, check the Uniden site...
http://www.uniden.com/scanners/icat/scanners_b2c/
It sure beats manually entering frequencies.