Features Vs [Power consumption and form factor]
Most of the speculation has been seemingly prompted by Apple iWatch rumours, and given substance by efforts from Samsung, LG, Motorola and - pre-dating the current smartwatch buzz - Sony. Samsung have taken the 'everything but the kitchen sink' approach, as have the other traditional phone handset makers with their watch efforts. However, not much is said about the existing Bluetooth LE watches that occupy another point on the features against power consumption graph.
Casio (G-Shock BLE) and Citizen (Proximity) make such watches, which give phone notifications, and allow you to 'page' your phone. Reviews suggest the concept (minimal 'connected' features in a traditional-looking watch with good battery life) is sound, but the implementations are not satisfactory (random breaking of the Bluetooth connection etc).
The other element in the mix are the type of device that some people have used for years - fitness trackers and heart rate monitors etc.
None of the above devices require a smartphone-class SoC or a colour display (The Moto 360 is criticised for using an OMAP3 SoC that is believed to be built on a 48nm process). Indeed, the Citizen Proximity watch uses only physical dials to show calls, SMS and email notifications.
The original iPhone was notable for what it left out (contemporary rival handsets had 3G cellular, copy and paste, 3rd party applications) as much for its multitouch UI... this might prove to be a good approach with watches.