I find myself wanting to call people once in a while, and I also find that I know people's twitter names pretty well.
What is disappointing is that none of the tools I have let me "dial by twitter name" in the sense that there's no command line prompt that has a "call" verb which takes the twitter username as an object.
% call @vielmetti
Actually, I'm at even a worse spot; I don't even have a "call" command to start from at the shell script prompt. However, Twitter is in a good spot to do this – it knows the cell phone number of a lot of its users.
Perhaps then this is too good of an idea – does following someone mean that you are expecting to get calls from them? Some measure of opt-in seems appropriate, lest that eggbot spammer direct dial you to sell you air duct cleaning.