Battery Buddy?

["PJ McGarvey" <pj_mcgarvey@hotmail.com>]

Anyone try using one of these - it's basically a separate battery that 
avoids getting discharged as fast as the main battery, and allows enough 
juice to get the car started?  Since I started walking to the train 
recently, our second car doesn't get as much use, and the cold weather is 
making it harder for it to start after sitting for a few days.  Worth the 
investment?

Thanks,
PJ