Not replied

I recently came upon a problem I was having with pretty much all messaging apps I use.. I'm a lousy replier!

I have many friends and family members on the other side of the world that I communicate with most days, and I don't always have time to chit-chat when someone messages me. Sometimes it will be 3am and I'll receive a message from my brother, and in my tiredness I will open it, half-read it, forget about it, and not see it again until he writes a second message. This is a problem for me, since there are only systems in place for 'unread' messages.

I want to know which messages I have not replied to yet. Simple.