That's right, there is more money in Bluetooth headsets and phone cover cases than in smartphones proper. According to researcher ABI, the market for smartphone accessories will hit $32 billion in 2007, much more than the $28 billion expected from the smartphone market.Roughly three-quarters of the accessory revenue will come from sales of "after-market" accessories, i.e. accessories sold separately from smartphones.

Here is a look at the booming accessory market:

Vendors and carriers alike are focusing on this growth segment because accessories typically carry high margins and serve to promote brands. Carrier interest, in particular, is driven by the fact that accessories offer consumers the opportunity to expand their use of their mobile handsets and service, leading to higher ARPU, the market analysis firm said.

Both Nokia Corp. and Motorola Inc. are pursuing the accessory market by emphasizing that the add-ons help subscribers fully utilize their handsets' capabilities as well as allow personalization of one's mobile use.

So you can expect Verizon and AT&T to battle Nokia and Motorola for the right to sell and brand your new headset and slipcover. Will carrier soon begin to subsidize smartphone accessories as a way to retain subscribers?

What do you think? How many of you buy accessories and add-ons for your smartphones? And which accessories do you buy? Bluetooth headsets? Smartphone covers? Let us know all about your smartphone add-ons.