$80 built, $55 for the kit. Pre-order: click here. This is the Stylophone Twenty Ten style. At 1:20 minute in one the video above is where you realize you want this over a software plug-in!
“The Nebulophone is an Arduino based synth with a stylus keyboard. It has adjustable waveforms, a light controlled analog filter, LFO, and arpeggiator that can be clocked over IR. This is a beginner kit and does not require an Arduino programmer board.” – bleeplabs.com
For more info: bleeplabs.com