Is there anything capable of doing a disconnect (radio or internet) based on periods of innactivity as opposed to designated times?

1) Radio control slows network searches to one per hour based on how long the network has been unavailable.

2) Internet diconnects automatically after a specified period of innactivity in case you forget to disconnect (perhaps 15 minutes would be a good default time)

The purpose of both of these would be to save battery power. The Treo 600 uses the most battery power when either 1) searching for a non-existant signal or 2) connecting to the internet.

Please advise.