Once you start taking time on how fast you can "stack cups" it first becomes really fun. Here you have the official competition hours from Speed Stacks, approved by WSSA. It's the new GENERATION 5 and it measures accurately (down to 3 decimal places) and is reliable and comes with supersensitive start and end buttons and digital display.
There is also a data port for external display and the new memory function allows you to save your best times and which dates you performed them. Comes complete with batteries.