The one I've had on my radar is called North Paw[1] (from 2009, five years after rincebrain's article). It's been on my list of things to try for a while. But that build is 10 years old now and as a result it's huge—it looks like a house-arrest ankle bracelet.
We've been through a decade of electronics miniaturization since then (thanks to cell phones), so I feel like it should be possible to make it more discreet. Does anyone know of an updated build? I'm an amateur when it comes to electronics so I could use any help I can get.