If you've considered an Apple Watch then I'll give my requisite recommendation to look at a Garmin. It won't have quite the features that the Apple watch does - but it's perfectly usable as a standalone device, has a battery life long enough that I don't even think about it (think week(s)), and has amazing built-in GPS.

It can potentially be more expensive than a Pebble, but competitive with an Apple watch, if not cheaper (depending on model). As a fitness tracker and notification machine I'd say it's superior to an Apple Watch - I haven't had an Apple Watch but have had android wear devices which seem to be about the same in terms of battery life and functionality.