In particular, here's what I'm looking to do: a location-based mobile app that connects candidates and employers. How?
* Upon sign-up, you self-designate as a candidate or employer.
* Based on your selection, you complete a profile about yourself or your company and the positions for which your company either is hiring or typically hires.
* Determine how closely matched you'd like to be with a candidate or employer on a 10-point scale.
* Choose to receive a notification via text message, e-mail, or both when you come within a certain number of miles of a "matching" (as defined by you in the previous step) candidate or employer. The message would include a link to the other party's profile.
* Within this text message and/or e-mail would also be the option to set up a meeting with the matching candidate or employer.
* If both parties agree, the meeting is set and added to their calendars.

Answer:

Actually, it's not just a mobile application. You have here server side, database, some statistics / backoffice to monitor user activities, integration with sms delivery service.

To begin with you need to define your requirements in a form of Functional Specification document. Based on this document you can see what should be done, realize the amount of work, time and cost.