The SPOT satellite locator beacons are pretty good for sending email/SMS with GPS position. In emergency mode it keeps sending every few seconds and also sends the position to some central control room which then passes it onto the MCA. You can program the message with your details (A/C reg / name / phone etc...) so this is also included so straight away they would know what aeroplane to look out for.
Plus people can track your flights on the web with a position sent every few minutes. No huge satellite phone charges and does not rely on GSM so works pretty much everywhere.
Not ideal on its own, but combined with a PLB could be pretty useful.