Anybody know anything about them? My sister has implied that she'd quite like one for her birthday, but my knowledge of them is pretty much zero. Basically, i know the iTrip is the most well known/popular, but apparently it's one of the worst as well

So, any personal or professional experience on which ones (if any) are good? Bear in mind that i'm not willing to pay a great deal (i don't love her THAT much)