Idea Validation

Hello everyone! I'd like to get opinions about this idea before starting to work on it.
as a person that attends gym regularly, i oftentimes doubt if i do the exercises right. so i thought of this idea of making an app with a feature that scans how you do an exercise and tells you if it's wrong, and if it is, explains how to do it and shows visually. i dunno if this idea is worth starting or not as that'd be a big project, so i'd like to get opinions from people. what would make you use the app? do you have suggestions? i appreciate honest answers :)