Just about anyone can do this for much less then 25 bucks. With this and this we are talking less then 5.00 really, albeit only detecting outages, add a MySenors board (another 10 bucks) and you have a communicating system (for those who have that infrastructure already setup) that will push alerts to any number of people.

If one wants to get really fancy, use a simple encoder, and CT circuit on the same MySensors 'board' and you have a monitor (not just detecting outages), and current sensing system for printer state detection (no need to hit a reset switch on every start) along with a communication system, all for around 40 bucks.

I know it sounds like I'm hassling you over your project, and perhaps that is a bit true. I'm not saying your product is bad, I'm just saying for ME the ROI is way to low. For those that lack the motivation/time and have the money to spend; your product looks like its perfect for simple filament movement detection.