Roaming between countries and across network providers lets users stay in touch all the time, but users can easily run up large monthly connection charges, especially if they travel internationally. The point might be moot for US users because US cell-phone providers tend to drive down charges for local calls but apply heavy tariffs for international usage, so most people simply don’t use international roaming. Throughout the rest of the world, however, international roaming charges aren't too excessive as long as users don’t overuse the device. For example, a week’s roaming in the United Kingdom costs me the rough equivalent of $47. This price might seem expensive but I send and receive a lot of messages and find the cost worthwhile to keep connected.
General Packet Radio Service (GPRS) roaming is possible only if your home provider has an agreement with a local network provider. Users can sometimes connect through Global System for Mobile Communication (GSM) when roaming agreements between providers don't permit full GPRS connections. (If your users connect to a GSM network during travel, advise them to scan for available GPRS networks, just in case. Most countries have at least two or three competing networks, and the chances are that at least one can support GPRS.) When users are limited to a GSM network, Research In Motion's (RIM's) BlackBerry lets them use the device's built-in cell-phone capability to send and receive Short Message Service (SMS) messages only—not email messages—to other BlackBerry devices or cell phones that support SMS. Furthermore, US GPRS networks use different frequencies than European and Asian GPRS networks use, so users can't yet enjoy full cross-continental roaming. (RIM plans to introduce triband-GPRS models sometime in the future, which will let users roam around the world with their BlackBerry devices—subject to roaming agreements, of course.)
