Backstory: A friend recently started coaching high school wrestling and wanted to keep stats on how his team did against each other in practice and at matches. He couldn't find anything and ended up creating multiple spreadsheets to track the data.
The Idea: CMS who-beat-who tracking software for coaches.
Deep Dive: This one would be relatively simple to build, you would give users the ability to input athletes, their opponents and scores. You could take it a step further and add notes and rankings. You could add a graphs and a visually stunning dashboard as a premium feature.
Validation: My friend needs it!
Monetization: You would follow the freemium model and have a simple/free version and then offer premium features at a high monthly cost.