I too have been interested in this approach, and am working on finishing off a Bass I'm building that's piezo only.
For the bridge, I'm using an allparts ABM-style bridge with piezo saddles, and then that will be coupled with the mint box buffer to get the right impedance signal to my amplifier.
Using the piezo buzzer type of transducer doesn't really work that well on a solid body instrument (at least in my experience), as there's little or no resonance for it to capture. I'd agree with Bass-Adrenaline - the results from Graphtec and RMC are pretty impressive!
I've got a thread that is (slowly) going in the Luthier's Corner, so feel free to follow it!
The diary of a procrastinator's second DIY Bass
Also, check out some of the work by Tom Clement, a luthier who makes good use of piezo 'pickups' in his Basses.
Hope that helps!
Dan