no, I don't want to write a keylogger

I noticed that Android is probably last mobile OS that doesn't convert national (unicode encoded) characters to english ones on the fly when used in SMS.
I was thinking about an app that would reside reside between software keyboard (stock SenseUI for example) and messaging application and convert national characters like Ś, Ą and make them english ones S, A so I could get 160 vs 70 max characters in SMS.
The other method could be positioning after the messaging application and convert during sending out, instead of typing in like in the first case.
Could it be possible to code?
No, I don't want to code my own keyboard or messaging application
