I use a Cross Ion pen attached to my keychain as it is one piece. Just pull to extend the point. If Cross would make a fine point gel refill, I'd be extra happy. Rotring makes a fantastic telescoping ball point.

As a pen addict, I've seen the Inka site but wasn't much intruiged. My keychain used to have a neat modern design pencil on it, similar to the Inka, but the core lead/pencil section got lost and I was left with the lonely holder dangling next to my keys.

At my cheapest, I attach a keychain sized Pilot Hi-Tech C pen http://www.jetpens.com/index.php/cPath/21_82 to my notebooks. They're available at the Kinokuniya Stationary Store in SF's Japan Town (if you haven't been here Merlin, guard your credit card). Actually, they have an entire line of mini-pens and pencils with little cell-phone charm loops (really, this is just an eyeglass holder tied to string for most). The cost $3.30 each and come in many colors. SF South Bay residents can get these pens at MaiDo (look it up on Yelp.com)

Pen Lust, oh yes. Levenger's having a sale on their pens, too. Can we just call it sharing instead of enabling?