I was trying to work out how to type in arbitrary text during a live show and have it displayed (in my case on a Laserworld CS1000RGB laser or on multiple laser/projectors). I have got it working on Windows so I thought I would share...
I ended up using TouchOSC (on Windows, but runs on Android, iOS etc) from Hexler (£15 to avoid nagware for Windows and £5 for Android). You get to design controls in the TouchOSC app and the OSC messages are sent to other computers (via IP address/Port) when controls pressed/slid etc.). TouchOSC comes with a sample keyboard template and you configure it to send the text box containing keys you press to the OSC message /group3/text2. Its straightforward to get an MM text control to listen for that OSC message and fill the MM text field (see attachment).
The end result is that I can enter any text and have it immediately displayed on multiple output devices connected to multiple instances of MM. You can backspace/clear and those changes are reflected in the output.