According to ABI Research, mobile Internet devices -- or MIDs -- are set to grow at a compound annual growth rate of 167% in the next five years. Wi-Fi, WiMax, and UWB will play a role in that growth, and, says ABI, so will Bluetooth. Why? VoIP calling, among other reasons.MIDs are small computing platforms that offer a nearly constant connection to the Internet. They also may include features such as media playback, gaming, location-based services, and social networking.

Powering MIDs' connection to the Net will be a myriad sampling of wireless broadband technologies. MIDs will be able to take advantage of Wi-Fi, WiMax, and possibly EVDO/HSDPA 3G technologies to reach the Internet. "All Mobile Internet Devices will feature Wi-Fi from the start," said ABI Research senior analyst Douglas McEuen in a prepared statement. "That is the essential form of wireless connectivity that no MID will be without."

Since Bluetooth isn't used to connect to the Internet, you might wonder why it would be all that relevant in a device that is focused on accessing the Web. Think about Skype. Any VoIP service that allows the end user to make phone calls through the Internet is going to find a home on a MID, such as the Nokia N800 Internet Tablets.

Holding a MID to your head, however, isn't so appealing. ABI says, "While many MIDs will include voice capabilities, they are larger than mobile phones, and for convenience some users will carry a low-cost phone as well. However, many consumers still want an all-in-one device, and the handset/headset configuration enabled by Bluetooth will meet their needs. That will be one of the main rationales for its early adoption in MIDs."

Any gadget geek -- or, heck, anyone else, for that matter -- is always going to have a separate mobile phone, even with the availability of products such as VoIP-enabled MIDs. I don't see Bluetooth-equipped MIDs replacing cell phones at all. Perhaps some professionals will use them to make long-distance phone calls when traveling overseas, but who's going to want to have to use a MID to make calls on a regular basis? Not me.

Even so, including Bluetooth in MIDs -- which ABI says will hit 95% penetration this year -- will enable all sorts of different and interesting usage scenarios.