NoteOn is a project to develop a small, self-contained smartpen. All currently available smartpens require special paper or a base station that clips to the page, making them inconvenient for quick notes and everyday use. NoteOn aims to be completely self-contained, using inertial measurement to track pen movements.
That's the plan, anyway. NoteOn is on hold in the firmware development phase. Getting the firmware working proved more difficult than I anticipated, and I lost interest in the project as a result. At this point, I don't think I'll continue developing it. Please feel free to develop or incorporate NoteOn into your own projects; the design files are licensed CCv4-BY-SA, and the firmware is licensed GNU GPLv3.
Currently, the electronic design of the first prototype has been completed, and two prototype PCBs have been assembled. Drivers for all on-board peripherals except the bluetooth transceiver have been written and tested.
This project was an entry in the 2014 Hackaday Prize, in which it advanced to the semifinals. As part of the entry, all project documentation is on Hackaday.io. Rather than repeat it here, I refer you to the NoteOn project page.