Some Suggestions about a Battery Tender?, I'd love to hear from everyone! Options

[snowbunny]

Ok, so I have a wacky schedule with my job and it takes me all over the US for seminars and stuff, which unfortunately leaves my poor car at home, not being started for 2 weeks, sometimes 3 weeks on end!
This is my problem, My car wont start after sitting for 2 weeks,
I know my first suggestions should be to check the battery, check the alternator.
But I am pretty sure those things are still kickin',

Should I install some sort of Battery Tender, or Battery trickler?
Or any other suggestions?
*I have asked my roommate to start it, but recently we were both gone for 2 weeks, and it wouldnt start then, since it sat there the 2 weeks we were gone, AND its kinda weird asking him to start my car every couple of days while I'm gone*

So please send some suggestions my way!!