I use a Fitbit flex 2 for that purpose. I doubt they make that model anymore, but probably make something similar. The flex 2 is just a little lozenge-shaped thing that tracks movement, can vibrate, and has a few little lights. The app let’s you set alarms (you turn it off by tapping it). I also have mine set to vibrate when I get a text message or a phone call in case I’m someplace noisy and don’t hear it.