If you're not interested in an Android Wear watch (or any other kind of smartwatch with a fully customizable/interactive display), then consider the
Martian Notifier, which is pretty basic, but gets many good reviews for its simplicity and effectiveness.
If you do want an Android Wear watch, then you can probably find the 1st generation ASUS Zenwatch or Moto 360 for under $100 these days (as a refurb).
EDIT: Here's the Zenwatch for $65 with free delivery on eBay:
https://forums.androidcentral.com/e...%2F272017471673%3FrmvSB%3Dtrue&token=vjQsVstn