Whenever I travel on business with a laptop I always ensure I have several internet connection options so there is an alternative if a WiFi connection fails or I feel I will be overcharged for an Ethernet connection.

Mostly that means I also travel with a 3G wireless data card built-in to my laptop or as an add-on peripheral, in either USB, PC Card or PC Express Card format. These wireless modems let users connect both to the internet and to corporate IT systems over 3G cellular networks, even if no WiFi or Ethernet cable connection is available.

But, as I have been discovering, a new class of devices, called 3G wireless routers, can make 3G data­cards even more useful, either as a back-up for cable or DSL broadband connections or as a way to extend and share a wireless data connection with other users - for example, at an offsite meeting.

A 3G router - sometimes called a cellular router - works just like a WiFi router, providing connectivity to wired or wireless devices using a 3G cellular data card as usually provided by a mobile phone operator instead of a fixed-line DSL or cable broadband connection.

I have been testing three 3G wireless routers - each for slightly different markets - as well as a clever little device called Windy 31, a plug-in USB stick that functions as a WiFi router or ac­cess point so the user can share a wired or wireless internet connection quickly and easily.

Windy 31 (www.synetusa.com) costs $60 online and lets users connect up to 32 WiFi devices to one host Windows-based desktop PC or laptop. Set-up could not be easier. The built-in software automatically fires up when inserted into a USB port. Users can then configure settings, including the network name and security features.

As well as enabling users to share an internet connection, the Windy 31, which comes with a convenient mini docking station, is also an easy way to connect other devices such as wireless VoIP (voice over internet protocol) phones and games consoles to an ad hoc network.

The Windy 31 supports the 802.11g WiFi standard, but the three 3G wireless routers I tested all support the faster 802.11n standard. Since 3G wireless routers emerged four years ago, they have become faster, cheaper and easier. The first 3G wireless router I came across was made by D-link and sold under the Kyocera brand. Initially the main users of the KR1 and similar devices were mobile work teams, emergency response units and corporate commuter vehicles that provided a connection to the internet for people on the move.

But newer, cheaper devices, such as Kyocera's KR2 (www.kyocera-wireless.com ), appeal to a broader market, including business users who just want to set up an ad hoc WiFi hotspot. The KR2 works with EV-DO (evolution data optimised) network cards and a much bigger range of 3G USB, PC Card or Express Cards. I have been using it with a Verizon Wireless 3G PC Card and have been surprised by the quality of the data connection, even in poor reception areas.

But, as with other 3G wireless routers, it is important to download and install the latest software that runs the device - the "firm­ware" - and check that it works with your 3G wireless data card. Like most traditional WiFi routers, it features four standard Ethernet ports to support hardwired PCs, video game consoles, media servers and other devices, in addition to WiFi connected devices, and it costs about $210.

The KR2 is made by Cradlepoint Technologies and is similar to Cradlepoint's MBR1000, although the MBR1000 lacks a PC Card slot (www.cradlepoint.com ).

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Cradlepoint pioneered a technology called WiPipe, which aims to make the best use of available bandwidth. The MBR1000 works with both EV-DO and HSDPA (high-speed download packet access) networks worldwide and supports a wide range of USB and PC Express Cards. It also supports the latest WiFi security settings and delivered good ranges for an 802.11n device in my tests.

However, my favourite feature is its ability to operate as a standard cable or DSL router and provide a back-up - or "failover" - service if a fixed-line broadband connection fails, something my home cable connection is certain to do as soon as I leave home, generating calls for IT help from my wife.

The MBR1000 is easy to configure. I plugged my home cable broadband connection into the device and a Sprint 3G EV-DO USB modem into another socket. When the cable connection was cut, the 3G card took over automatically to keep my home network connected. This feature makes the MBR1000 ideal for home office or small business use or for anyone who cannot afford to be without a broadband internet connection.

The third 3G wireless router I tried is a pocket-sized, battery-powered device des­igned for anyone who might need to set up and configure an instant WiFi hotspot. Cradlepoint's ultra-portable PHS300, dubbed "a personal hotspot", costs $180, works with either a 3G USB card or "tethered" 3G phone - when the phone is connected to the router with a cable - and is powered by a rechargeable battery, making it possible to set up in locations without mains power for several hours. It comes with built-in firewall software to fend off snoopers.

While 3G wireless routers may not appeal to everyone, they do provide an additional use for 3G cards and enable their owners to extract more value from the often costly "all-you-can-eat" monthly service plans that most network operators require.

paul.taylor@ft.comVisit Paul Taylor's new forum where he answers your questions on gadgets, gizmos, software and services at http://blogs.ft.com/gadgetguru