Develop a social media blocker

I need to someone to develop a productivity tool to switch off social media distractions such as facebook and twitter while working, for a specific time duration that the user can choose. the only way to get round this ban will be to reboot computer. I have a website that has a number of subscribers who will find this useful, and I plan to have other tools developed if this is a success. I may also want it developed for Windows OS. Budget is limited so work with me