Global crowdsourcing platforms could offer new employment opportunities to low-income workers in developing countries. However, the impact to date has been limited because poor communities usually lack access to computers and the Internet. This paper presents mClerk, a new platform for mobile crowdsourcing in developing regions. mClerk sends and receives tasks via SMS, making it accessible to anyone with a low-end mobile phone. However, mClerk is not limited to text: it leverages a little-known protocol to send small images via ordinary SMS, enabling novel distribution of graphical tasks. Via a 5-week deployment in semi-urban India, we demonstrate that mClerk is effective for digitizing local-language documents.