Post contextual reminders on web pages.
Prospective memory helps us remember to perform an action in the future. We often use physical locations and cues, to remember daily activities like taking pills, or walk the dog. In digital spaces, there is often no equivalent device.
PM is a chrome extension that allows reminders to be contextually placed in a browser location. You could use a reminder to send a message to someone in gmail, make notes on a web app you are developing, github project page, or leave "guilty" notes in places we go when not working (reddit, hacker news, etc).