Did you ever play one of these?

[MmmPedals]

http://www.effectsdatabase.com/model/morley/saw
I did 
Its SOOOOOOOOO cool. A local shop had it. Its a belt clip on pack with a metal pick attached (thats the PIK on the schematic). The EV reacts to your picking.
If there is demand i can probably get gut shots.

[alparent]

This thing looks cool! Did you get it or just try it in the shop?

I guess this could be easily cloned.

Having gut pictures would be great.

[RickL]

I've got one, or at least something similar from the same series and it is the best tracking auto wah I've ever played. The pick triggers an LED that fades in (or out depending on the particular effect) with the fade time set by a pot. The LED shines on an LDR that controls the filter, or in the case of the "Slow Gear" type effect, the attack time.

I've built a couple of variations of the filter and attack effects on perfboard and they are small enough to fit into little jewellery boxes that I've picked up over the years (maybe 3 inches square).

I'm pretty sure there is a very similar project posted on the site that includes a layout - maybe it's for the attack version.

[frequencycentral]

Why guts? There's a schematic linked to from effectsdatabase: http://www.morleypedals.com/sawes.pdf

[alparent]

Why guts you ask?   'Cause I didn't notice that link! 

[puretube]

Lubow, again...