On Second Thought lets you do this. Currently out for Android, though I think there's an iPhone beta right now.
Seems like you could (on iOS) follow the same red underline for words that aren't found and then tap to see suggestions/replace - except you would do this in the actual message "bubble". Making the user type the actual word they meant and ALSO an asterisk is a lot of work.
I really like this concept, especially the interaction for case 2.
I think a better solution for single word correction is just always show the word to be replaced in blue, if user agrees he/she can tap the blue word to execute the replacement, rather than it being replaced automatically for the need of an undo mechanism.
And for multiple matched words, as in case 2, I think it may be better to highlight all the matched words and wait for the user to tap on one of them, since he/she may not have paid attention to the quick flashing words and missed which ones were tappable.
And if no correction is needed, the next message sent by the user will cancel out the highlighting, ending the interaction.
I really appreciate it. I do the same whole day and seeing that it will correct the text without adding more effort. I like to see how it feels on Whatsapp or Messenger
Well then I hope automatic correction after asterisk won't go wrong.