Mark,
Technically, a boot loader is a program that gets programed into the boot section of the chip. When it starts up, the boot loader program is the first to start, if it doesn't get any information from the computer in a certain amount of time, it starts the actual program.
That would work though as a usb programmer. Its alot like that programmer I have. I took mine apart to see how it works. Its an amtel at90usb series chip.
I have not gotten too much official testing of my controller besides just driving around the yard and up and down the street in the golf cart.
I do have a few other things in the works that I think will be liked.
-Adam