check out the Spider Capo... I have 2.. they take partial capo-ing to another level... you can block whatever string you want and leave the rest open... I have something new based on having one capo at the 1st fret with the E and B raised to F and C, then the other capo at the 7th fret with the D and G blocked giving A and D octaves... so the tuning would be F A A(oct) D(oct) C E... the cool thing is the guitar stays in standard tuning and I play on both sides of the 7th fret capo..
anyhow, there are hundreds of variations... a couple of players from Woodstock NY are selling them...