I've experimented with adding e-tips to the thumb of handknit mittens with conductive thread. It was somewhat successful, although I think I didn't quite put the pads in the right place so I have to kind of roll my finger around a bit to get them to engage. It does work though.
I did it by embroidering a little pad on the thumbs of some mittens with conductive thread, although another method is to knit the thread straight into the fingertips of the gloves. (I think this would eliminate the placement issue I had, although I've read that embroidering results in a more conductive material, because you can use the thread more densely).
I bought the conductive thread on Etsy. You can get it from lots of places, but Etsy had sellers that sold small quantities rather than an enormous spool.
ETA: Here's a tutorial:
http://www.blogher.com/diy-tec.....ive-thread