Silent Presentation Timer is the most unobtrusive presentation timer, lecture timer, or meeting timer ever. Just keep the phone in your pocket and feel the silent vibrations. I use the timer during my own meetings, presentations, and lectures and I have been developing it using my own presentation experience.
And all this is for free, without ads.

Features:
- full Android Wear/smartwatch support, application runs on phone as well as on Wear
- ambient low power mode support with special presentation visualization on the Wear device
- configurable length of presentation/end time of presentation
- countdown presentation timer with visualisation
- green (lots of time left), orange (lots of time passed), red (close to end) indication of the time left for your presentation
- optional measurement of overdue time (violet)
- presentation timer can run in background
- runs if you put the phone to the sleep mode - set the timer, run, and put your phone sleeping to your pocket
- runs even if you switch to another application and the intervals will be still indicated by vibrations
- change of phone orientation or incoming call will not stop the presentation timer
- optional screen dimming (to save battery if you disable sleep)
- optional disable of the phone sleep mode

User's guide: http://papacut.sweb.cz/dt_wear_users_guide_international.html

Have fun and enjoy your presentations!