What are you and the fellow that you may have a "possible colaboration" with trying to achieve?
I only meantion this because MIDI and electric bass are hard bedfellows- not impossible, mind you...just difficult. It CAN be done, but it's gonna take some capital, patience, and a bit of schooling to get things right...and even then, you might be in for some small dissapointments here and there.
MIDI doesn't like bass strings, especially the low E and B strings. The others are OK, but that's it.
You have to have a pickup that can differentiate the different strings when dealing with MIDI- reasons being is because you can't hit two notes with one string simultaneously: MIDI hates this and will freak out, not knowing which note is the right one. As with any multi-string instument, you will hit mutipule notes at the same time, even for a fraction of a second. If you were to plug your bass with normal pickups into a MIDI board, it would freak out over A.) no constant gain/volume of the string B.) no constant tone of the string C.) unfamiliar octaves. The other reason is that MIDI NEEDS the string to string processing power to handle a bass's strings. More power dedicated to one string, the less tracking issues.
So, it really depends on what you (and your friend) are looking to get out of such a setup. If you're looking to do some really cool effects but don't wish to delve too deep into it, a Vbass is the way to go. If you want more options, then a GK or other pickup examples that GreenBoy has meantioned will work with other type of 13-pin readers. If you wanna go all the way and hook your bass to a synthesizer, then you'll need some good stuff (including a mounted pickup or a more expensive bass with said pickup already installed), an interface, and a synth. BUT, be prepaired to find out that anything faster than "Mary Had a Little Lamb" in 4/4 time is gonna choke the synth for most tones....not all, but most...
Matt