PurrPad makes use of the Taptic Engine built into MacBook trackpads, so instead of hearing a purr through your speakers, you feel one under your palm. Developer Francesco Pavanetto, who shared the app on Reddit , says he tuned the vibration to the actual measured pitch of a real cat purr and built it so the pattern never repeats exactly. The app features six different cats, each with a distinctive attitude. House Cat is included in the free version, and it usually purrs when you rest your hand...
