Who knew but Windows Phone 7 has speech recognition capability built in! It can be enabled/configured from the settings screen under Speech (duh!), and can be enabled and enabled even when locked.
To activate hold the start button (Windows button) then speak items such as:
Call Roger Wilkinson Mobile
Open Calendar (start works as well)
I have tried with a few contacts and downloaded applications as well as preinstalled ones and games with good results. While it is not 100% accurate I have probably experienced around 90-95% success rate (admittedly trying to pronounce clearly, it is not as good if you don’t make the effort).
I would recommend giving it a try if you have a WP7 mobile, and I really can’t understand why this fantastic feature is not better advertised.