Those machines, however, get no cell signal on their own; you have to supply your own cellular modem. They’re also big and metal and ugly. But the real deal-killer is that they have to be plugged into a power outlet. You can’t use one at the beach or in the woods unless you have a really, really long extension cord.

The MiFi is remarkable for its tiny size, its sleek good looks, its 30-foot range (it easily filled a large airport gate area with four-bar signal)  and the fact that it’s cordless and rechargeable.

Image Novatel's MiFi, a 3G Wi-Fi router.

How is this amazing? Let us count the ways.

First, you’re spared the plug-and-unplug ritual of cellular modems. You can leave the MiFi in your pocket, purse or laptop bag; whenever you fire up your laptop, netbook, Wi-Fi camera or game gadget, or wake up your iPhone or iPod Touch, you’re online.

Last week, I was stuck on a runway for two hours. As I merrily worked away online, complete with YouTube videos and file downloads, I became aware that my seatmate was sneaking glances. As I snuck counter-glances at him, I realized that he had no interest in what I was doing, but rather in the signal-strength icon on my laptop  on an airplane where there wasn’t otherwise any Wi-Fi signal. “I’m sorry,” he finally said, completely baffled, “but how are you getting a wireless signal?” He was floored when I pulled the MiFi from my pocket, its power light glowing evilly.

If he’d had a laptop, I would have happily shared my Wi-Fi cloud with him. The network password is printed right there on the bottom of the MiFi itself. That’s a clever idea, actually. Since the MiFi is in your possession, it’s impossible for anyone to get into your cloud unless you show it to them. Call it “security through proximity.”

The second huge advantage of the MiFi is that, as with any wireless router, you can share its signal with other people; up to five road warriors can enjoy the same connection. Your youngsters with their iPod Touches in the back of the van could hop online, for example, or you and your colleagues could connect and collaborate on a corporate retreat.