Time and a word

[j4]

Does anybody know whether there exists a way of timing the writing/sending of a text message? Ideally it'd be some kind of stopwatch that you could set with a keypress and unset once you'd finished (so in fact you'd be able to use it to time other things on your phone as well, but call timing is already built-in for most phones and I'm not sure what else would be useful). Basically I'm interested to know how long it takes people to write and send (without using a template) short messages like "Yes", "No", "Thanks", and "Busy, will reply later". Obviously everybody's typing speed differs, so I guess I'd want to collect data from as many people as possible to get an average speed.