"I thought Voice Command was a service you could use with any Sprint
phone, not something you had to install. "
Confusing, eh? Sprint has a voice dialing service that resides on
their network.
But Microsoft also sells a software "Voice Command" that resides
directly on the phone. This lets you open programs, look up contacts,
check system status, and all kind of nifty things by merely talking to
your smartphone.
It doesn't come with WM5, you have to buy it for about $30 extra.
Most people find that it is well worth it.