Cell phone booster ???

When we go to the (recently-aquired) cabin we are just on the edge of cell
phone service.
We can get a signal less than a mile from the cabin, in terrain that is
heavily forested and has variances of elevation of no more than 50 feet
vertical
We really don't want to have permanent (line) phone service in the cabin,
but it would be nice to have cell phone service just in case

Someone suggested we get a cell phone booster for the car and/or cabin

Any advice and experience with such a device would be appreciated

Oh yes, primary service is T-Mobile
But Cingular is the provider in and around the cabin
The phones are Motorola Razor V3s
We also have some Motorola V300s that could be left at the cabin for 911
if
a booster is a solution