Turns out there isn't a way to do it -- unless you jailbreak your iPhone. Using Veency, a jailbreak app that Erica covered about a year or so ago, you can head into your iPhone from your Mac and do anything you want, from changing tracks in iTunes to even sending text messages. Here's an older how-to on getting it working.
Unfortunately, other than that (according to our research -- commenters feel free to jump in, of course), you're out of luck -- Apple is fine with sending commands from the iPhone to the Mac, but not the other way around. Maybe Bose needs to come up with a way for you to stream music over Bluetooth to their speakers so you can keep your iPhone with you.
Update: Our commenters come through as always: Rogue Amoeba's Airfoil will supposedly send audio from your Mac out to your iPhone, and while I haven't tried it myself, we're told that the Bose dock will then play that audio for you. So instead of playing sound on your iPhone, you can just send it music from the Mac and control things that way. And Jeff points out that Belkin makes a Bluetooth dongle, so you can stream music that way as well (and just carry your iPhone with you). So there's a few solutions to try.