This document proposes a mobile security solution on cloud that uses mobile phones as surveillance devices. It has 3 key components: 1) an Android camera application that takes continuous images from mobile phones, 2) a backend service that receives image data periodically from mobile devices and saves it to cloud storage, and 3) a web application for users to access and search image data. The solution aims to provide low-cost private surveillance with no installation costs by storing image data on Amazon S3 and user information on Amazon RDS, with processing handled by Amazon EC2 virtual servers. It claims advantages of lower costs, robustness over networks with low bandwidth, and practical long-term archiving of surveillance data.