TinCan[1] does that, at least with text. There was a discussion here a few months ago about using AFSK to control external hardware that spurred me to hack together a script that allows this (output only) on iOS Safari[2] and I use it to control some Arduino projects.

[1] https://play.google.com/store/apps/details?id=com.hubski.com...

[2] http://sixteenmillimeter.github.io/Javascript-FSK-Serial-Gen...