Good and Simple, Could Use Some Improvement

The timer works fine on OS X 10.10.2, using the system alert volume and sounds, as well as an alert window with customizable text. One can create several timers for different uses, and start/stop them from a menubar countdown (optional).
The GUI is clean and simple, with no un-nescessary art. That’s the way I like it. It seems to fit into the Yosemite GUI nicely.
When setting up several custom timers, they didn’t organize correctly based on duration. But, the menubar was correct, and when entering Preferences again, it was correct.
A Notification Center Widget would be a helpful improvement, as well as mutiple timers, and repeat timers.

SkyMakai about Activity Timer