Are you looking for live sound, too?
I have
the Digitech Vocal 300, and it's awesome. It's got a robot setting built right in, and you can mess with it to make it sound like whatever you want, and save the settings. It works just like their guitar pedals, so you can switch settings during songs with ease.
It's $200. I've had mine since just after it came out, and it's still held its pricetag. It works great. Plus, it's not just a robot voice, it's got any effects you could think of. The expression pedal lets you assign certain parameters to play with real-time, so you can adjust a delay, or volume, or whatever you want real-time, live while you jam.
It's awesome.
There's a $300 version out now, too with USB hookups being the only difference, for use with recording. Although, you can just use the XLR out to record with, too.
Worth looking at, at the very least, if you want to have effect like that live.