This is an old revision of the document!
Before I had the spiffchorder I used several different approaches to getting my 7 keys seen as an input device.
The 2 which were longest lived were a hardware modification of a commercially available but not wearable chorder and a Linux kernel modification.
These will eventually be documented here. In the meantime, you can see them at http://www.cs.vassar.edu/~priestdo/wearable.pics.html and http://www.cs.vassar.edu/~priestdo/chordhack/