App is free because the sensor is not – Backbeater Review

I have used a TempoRef for years and wanted to see what’s available for an iPhone app. This app is virtually useless without their sensor, which costs $60. Maybe I’m wrong but a piezo drum trigger runs about $20, so not sure what’s so special about their sensor. I’d love to try it in a live situation but not for $60.
Review by robgarbo on Backbeater.