On your Android phone, access the home screen where you want to add a Keep note. Tap and hold on the screen and choose ...

Rocketbook claims that any FriXion writing utensil will write and erase on its sticky notes. I only tried the pen included in the starter kit, a FriXion Ball gel pen with a 0.7 mm tip.

Antinote is a sticky notes app for the Mac, which makes it easy to take quick notes, start timers, convert currencies, perform basic calculations, and much more.