Most likely that getting WakeMate manufactured was a painful experience and he wants to avoid physical products now.

Most likely he got burned with the "real" world.

Perhaps that the real business of WakeMate is the software they build, not the wristband.

WakeMate had a disastrous launch where some of their USB chargers lit on fire. I think Gabriel doesn't want to deal with/feel he can help startups with these sort of problems that only come up when you're making a physical product.