Tension Software (www.tensionsoftware.com) has launched Counter 1.0 for Mac OS X. The app does one thing: it allows to count a discrete number of elements.
Using Counter you can solve any kind of situation where you have to computer enumerate a total number of elements (physical or abstract), and you want to be sure the process will be error free. You can add to the total a new unit simply pressing the space bar on your Mac to count it. Counter will keep track of the counting as it progress and will add +1 to the total at any space bar press.
Counter 1.0 requires OS X Yosemite or El Capitan. It costs $0.99 and is available at the Mac App Store.