The postman brought a Behringer Bass Synthesiser pedal to me this week. They're about $70 new on Ebay and do a good fuzz wah if you use an expression pedal. Also has some phasing sort of modulation settings and squelchy analogue sounds.
Boss also make one but it's not as good at tracking the notes. Also the Behringer has a pitch hold function. I guess you can hold a note and then use the direct output to play over the top -- a bit like the new Electro Harmonix Freeze pedal I'd guess. (Keen to try one of those.)
The Behringer also gets closer to the sound of an Electro Harmonix Q-tron pedal for that Higher Ground sound. Unlike Boss though, the Behringer is made of plastic.
The Boss's shortcoming in tracking a bass makes an interesting effect on drums though. It creates these somewhat atonal but quite bubbly generated basslines. It's very acid sounding and fun for jamming.