A Linux laptop can be used to collect data outside an office, e.g. geodesy data, sales data, network checks, patient data in a hospital and others. There is support for wireless data connections via cellular phone modems and amateur radio. I am not sure whether PCMCIA radio cards are supported, see Aironet Wireless Communications http://www.aironet.com/.
There are laptops available with cases build for a rugged environment (even waterproof laptops). In some environments, for instance in hospitals, take care of the Electro-Magnetic-Compatibility of the laptop. This is influenced by many factors, for instance by the material used to build the case. Usually magnesium cases shield better than the ones made of plastics.