The concept has been around from a long time. The most famous example of Crowd Sourcing is “Wikipedia”. Wikipedia, the most comprehensive encyclopedia is the result of the information created by writers and editors from the crowd. The various Bug Bounty programs run by Tech giants is a wonderful practical application of crowdsourced testing which reward researchers and software hobbyists for finding software bugs. Beta testing (many apps have beta versions available in play store / app store including WhatsApp Beta program) is also a form of crowdsourced testing where a set of end-users can access the application & provide their feedback.
Will you start testing in parallel with development or only after the development is completed? What about testing at the code-level? i.e. code reviews to ensure best practices are followed. Will it only be reviews or will you actually run the application to identify defects? How about utilizing some automation tool to ease the process? Or will it be hybrid?