Obtaining synth sounds on bass is a difficult task. Lately I've found a combination that sounds great by itself or for recording, but gets buried live. The main ingredients are a mastotron and a bass octave deluxe. Adding enveloppe filter after can get you the sound from Herbie Hancock's "Chameleon" pretty acurately. But again, depending on what your band is made of, it might get you lost in the mix. I don't know if dedicated synth pedals would do the same, but my educated guess is that they would.