In addition to the costs noted by Dr. Young for "investigator fees" you should also consider whether or not you have the proper operating framework in place across your organization to meet documentation and procedural requirements. Your entire SDLC needs to be validated before you can even begin to gather data about "efficacy" that you might want to use in a submission, marketing claim, or in support of a regulatory application in the future. Having released a mobile application in this space in addition to several web apps, I'm happy to discuss more details with you if you like :0)