Well, it SHOULD have bluetooth. Have you tried pairing your Iphone with it?
Why'd you say it's a $2800 Mac Pro if it's 3 years old and you just got it...?
Anyway, if it really doesn't have it, a small as hell bluetooth dongle costs like 5 bucks these days.
Also, please point me to a $5 BT dongle that is Mac compatible, cheapest one I've found is $15
Sorry, didn't realize they might NOT be compatible with a mac... Every device I've ever plugged in has just worked. Don't know about BT dongles specifically, they should be simple enough technology after all, so here's one that costs under 2 dollars if you want to take the chance:
http://www.dealextreme.com/details.dx/sku.11866