Video replay app

I want someone to build an app with similar functionility to an app called Video Delay Instant Replay available on Playstore. Will need to run on Android and IOS tablets and phones. Part of the project will be to improve on professional look, functionality, ease of use, etc. Developer must understand how to build live and delayed video cabablility using built in tablet cameras, with adjustable instant replay speeds (i.e. variable slow motion speeds). Will also need voice activated start and stop recording functionality. Will work with developer on other improvements in build plan.