If you haven't heard of him, the joke's on you. Maybe. In any case, his work is worth looking into. He has done interesting work in font creation, font building primitives, rasterization, 2D drawing, and resistant social network graphs (which turns out to be more or less equivalent to the Old Sk00l Google Juice system). He was recently instrumental in performing a wonderful experiment in editor building --... - Source: Hacker News / about 1 year ago

I'll update this if I find more. For now, this seems to be a partial solution. It's a Gmail add on (except I don't use Gmail) that adds reminders. The options when setting reminders include cancelling it if someone replies, and to remind everyone in the thread. If you combine those two, it seems like — if you use Gmail's web client and have $23/month you're dying to get rid of — a decent way to add the feature. Source: over 1 year ago