An SMS gateway is a device or service offering SMS transit, transforming messages to mobile network traffic from other media, or vice versa, allowing transmission or receipt of SMS messages with or without the use of a mobile phone. Typical use of a gateway would be to forward simple e-mail to a mobile phone recipient.  Some popular SMS gateways are FrontlineSMS and Clickatell.

Uses

An SMS gateway is an essential part of democratizing election monitoring projects and/or reducing costs by enabling reporting through mobile phones.  The gateway provides the link between the mobile network and computers.  It allows project organizers to import and manage SMS messages for analysis, mapping and other uses.  SMS gateways can be used to broadcast instructions and updates to mobile monitors.

SMS gateways were first used in election monitoring in the 2007 Nigerian elections (FrontlineSMS).  Clickatell has been used in many projects including the 2010 Sudanese elections.

Useful Links

SMS gateways on Wikipedia
Wikipedia’s list of SMS gateways
The Open Directory Project’s list of SMS gateways