One of those "presentation" mouses would hopefully do? They're a mouse but you hold them in your hand and wave them around to move the pointer, like a Wiimote but they pre-date the Wii. The mouse pointer part sucks in my experience but they do have two buttons and are comfortable to hold. Considering you're writing your own input parser you can ignore mouse events.

There are also "smart pens" these days with Bluetooth but I've never tried one.