Development of the service callback

Need to develop a service similar to this:


All the details can't say that wouldn't get leaked.
Interesting the estimated time and cost of implementing such a project. And what technologies/languages are planned to implement the project.
Desirable experience in implementing similar projects. Cooperation consider only formal contracts with a SP/LLC, the agreement States the fines and penalties for disclosure of confidential information.

Answers of the form "ready to take" just in denial.