[s]http://iprototype.nl/products/compon...Slide-Joystick
Would this work for a joystick? Or is it too big?[/s]

If I'm correct there's only about 8 mm left on each side of the device?
According to the data I found the motorola droid is 116 mm wide, the jolla 131. 15 mm surplus, which means 7.5 mm on each side surplus. That means no real space left for a d-pad.