Overview ​

Keypadder runs on your desktop machine and provides a mobile/tablet-friendly web page that you use from a tablet or phone to send frequently-used, awkward, or difficult-to-remember key combinations to the currently-focused desktop application.

Amongst other things, the author uses it with Thunderbird and LibreOffice Writer for typing accented characters, with MuseScore to provide a keypad similar to a certain commercial score writing application, and with Firefox for accented characters and Emojis in social media.

It's a great use for one of those old smartphones or tablets you have lying in that drawer!