You also need the striking content in your entire lead generation process, the content for email pitches and others, you must have an epic sales pitch to be successful also the content must be plagiarism free, another tool you can use for this purpose if you have someone else’s sales pitch ready, you can grab that copy and paraphrase the content, the tools make paraphrasing easy with just one click, go now to... Source: over 2 years 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