Google Maps for Windows Mobile just got updated to version 4.1.0. This version includes now the capability to perform voice activated searches. Just need to press Talk button and say what you're looking.
But not everything is great... for now, it only recognizes English, including several accents as Australian, Indian, British, etc, and Mandarim. In my personal case, in Portugal, if I ask for "restaurantes" it searches for "chris nolan". But if I say "restaurants", all is well.
In case you're wondering: "Falar agora" means "Speak now".
Donload available on m.google.com/maps, from your device's browser.