Cross-platform surveillance agent

We need to develop an agent that runs as a service on Windows and OS X, taking intermittent screenshots of the user's screen. It saves the screenshots to the disk or a database, but only if the screen has changed since the last screenshot was taken. The screenshot is discarded if it hasn't. After saving a screenshot, the agent attempts to upload it to a specified URL using HTTPS. Before the first upload, the agent sends a GET request to determine whether it has been authorized for uploads yet. If it hasn't, it waits for some time before asking again. If it has, it can begin uploading screenshots. Information uploaded along with each screenshot (e.g., via GET fields) should include (1) the logged-on username, if any; (2) the name of the computer; (3) a GUID that's uniquely generated when the agent is installed. If the agent has been authorized on the server end and the screenshot upload succeeds, then the screenshot is deleted from the disk or database. If the agent hasn't been authorized or the upload fails, the screenshot is marked as queued, and the agent will try the upload again later. I need native executables for the project, so using on a framework like .NET isn't an option. Please mention in your proposal what tools you would use to build the agent. I've considered Qt, Lazarus, and Visual C++, but ultimately, I'd like to use what will work best for you but can still create native executables. Appropriate installation packages for both operating systems also need to be built: MSI for Windows and MPKG for OS X. Finally, to confirm you've read these project details, please mention in your proposal what five plus three equals. Thanks, and I look forward to hearing from you!