The Band Pickup System
The Band Pickup System by Headway Products of the U.K. This is what I use for my gigs. It reproduces a live sound with an integrated piezo (ceramic) pickup, better than other piezos! The wrap around setup allows the treble and bass to come through nicely. It is fast to setup and take off and no other modifications are needed to amplify an acoustic instrument. There is no other better option I've found for amplifying an acoustic violin without having a dedicated built in pickup into the bridge. This setup is nice and easy if you are a concert/Symphony violinist but don't want two Violins (one acoustic, one Electric) otherwise you have to swap out your bridge which has its drawbacks.
Available for violin, Viola, Cello and Bass.
* I recommend using a preamp to boost the signal. It produces a cleaner sound and more "head" range. For example, a preamp is necessary if you plan on playing for bigger crowds or bigger setups. I use the Headway Preamp EDB-2 now and it's a clean, sweet sound with plenty of power to boost to most any board or house PA. The pricing on this is a bit higher than compared to other preamps however you benefit from the multitude of options and strength in clean signal which for me is a must. Plus, it has two channels and a iPod hookup for backing tracks so I can "one-man band" it if necessary.