So it seems like every developer has to have his own counting app. Here is my take on it. Enjoy it for free. Supports counting on Apple Watch and with a Today Widget (pull down from above, edit -> add widget), which you can access easily while working in another app. No need to switch to easyCount Free to make it count.
easyCount Free is synced so you can also increase the count with your Watch and use your iPhone as a bigger display to show the current score ... eg game scores.

Want to count with custom increments? Change the incremental value (hold the button in the middle on your iPhone/iPad or press the number on your Apple Watch) and add it again by tapping the button same button shortly. (needs upgrade)

Whatever you want to count - you can count on easyCount.

Count down
Count up
Count
on
it