A mobile-broadband modem is a thumb-sized gadget that slots into a laptop computer’s USB socket to provide wireless internet access where there is a mobile phone signal.

Such devices make use of the same networks as phones, relying on the 3G phone network for fast data transfer. The technology is not new but the Mifi from mobile network 3 adds a novel twist – it’s a mobile broadband modem that acts as a wireless network access point.

Where standard mobile broadband modems work with just one computer at a time the Mifi can share its wireless broadband access to several nearby devices as long as they can access a wireless network.

So, if you are out and about with others, turn on the Mifi and it will appear just like any other wireless network. Anyone with a laptop or suitable mobile can connect to it for internet access and there is a password for security.

In addition to the cost of the device there is a continuing cost for use: on pay-as-you-go it costs around £10 for each gigabyte downloaded, or a monthly contract offers 5GB for £15.

With the size and appearance of a small tin of mints, the Mifi is easily pocketable. Indeed, once it’s on, a pocket is as good as any place to store it. We found the useful wireless network range to be around 10m indoors through walls, and a good 20m outside with no obstructions.

The download speed depends on several things, not the least being signal strength. The Mifi’s theoretical maximum speed of 7.2Mbits/s is let down by Three’s network, which has a maximum of 3.6Mbits/s, and that itself is an ideal figure unlikely to be achieved in real use.

We regularly got 2Mbit/s in London, but elsewhere in the country the speed was often barely a quarter of that. Still, that was broadly acceptable for everyday web tasks.

Less acceptable was the Mifi’s battery life. Its maker reckons it is good for up to five hours’ active use but our test unit’s power regularly ran dry after just three hours with multiple users connected. It can be powered and charged through a USB connection, though, which helps somewhat.

Getting connected was also annoying, with multiple button presses required each time the Mifi is used. There are dedicated buttons for turning it on, connecting to the 3G network and powering the wireless network. Given its single purpose this is needlessly complex.

Those gripes aside, the Mifi is a niche gadget but a good one.