I have two Cingular phones paired to my car's Bluetooth. Mine is a Treo 650 and my wife has a Motorola V551. Whenver my phone pairs, it looks like a small phone (which looks surprisingly similar to a Treo). When my wife's Motorola pairs, a triangle appears.
There was recently a firmware update for the Treo 650. Prior to that, my Bluetooth wouldn't show the signal strength on the iDrive screen. It would simply show that "tower" if I had a signal, or it would disappear if I lost signal.
My Treo has never shown a triangle on the screen and I have no missed calls.
2008 BMW 535i Space Gray, Black Leather, Dark Bamboo Trim| Sport Automatic with Paddles | Sport Package
2008 BMW M5 (gone, but not forgotten) Space Gray, Silverstone Merino Leather, Madeira Walnut Wood Trim | 7speed SMG | All options
Mods: Corsa Exhaust | RPI Ram Air Intake | H&R Sport Springs | Rogue Engineering 12mm spacers