Also doesn't Linkedin already do this. They have a search engine you can use to filter out applicants based on school, past experience and location. I also believe they released a lite version to make it more affordable.
Some startups you should look at if you're interested in this space: Hired.com, Whitetruffle and Wayup.com (they introduced a way for companies to post requirements and get paid per qualifed applicant)
We only do sourcing. https://www.shrm.org/resourcesandtools/tools-and-samples/hr-...
You need to connect with someone to get their contact info and you'd be surprised how hard it is to get emails of engineers.