4, you can get a portable Apple Watch charger that doubles as a keychain for $29 off the usual price — you'll Pay just $19.99 ... When you compare it with, say, the Garmin Vivoactive 4, the Apple Watch comes up short by about a week of battery Power ...One of these convenient Apple Watch keychains is typically $49, but you can snag One for only $19.99 for a limited time.