Interactive planner
Ultramarathon GPS Watch Battery Planner
Test race time, starting charge, finish reserve, and contingency against separate manufacturer-published GPS modes.
Free research tools
Turn product research into a decision.
Interactive tools that turn scattered specifications and review evidence into a clearer next step. AI organizes the data; Ben Yardley checks the sources, assumptions, and limits before publication.
Working tools
Use the research, not just the conclusion.
Each resource handles a different part of the purchase: race-day battery planning, terrain-and-fit shortlisting, or like-for-like specification comparison.
Filterable evidence matrix
Trail Shoe Terrain & Fit Matrix
Narrow ten researched trail shoes by terrain, forefoot shape, cushion, distance bias, and drop—without turning fit into a fake universal score.
Normalized specification data
Running Headphone Specification Database
Compare fit format, weight, single-charge battery, case totals, resistance rating, controls, and awareness approach.
The contract
What a Phavai tool must show.
Every output shows the assumptions that produced it, so you can change the decision instead of trusting a black-box answer.
Manufacturer facts, independent tests, and owner observations are labeled separately rather than blended into one unsupported claim.
Conflicting measurements, older generations, and evidence gaps remain visible. The tools narrow research; they do not manufacture certainty.
How these resources are built
- AI assists with organizing source material, normalizing fields, and checking internal consistency.
- Ben Yardley reviews the published inputs, calculations, evidence labels, cautions, and links.
- Interactive results run locally in the browser. No account, upload, or personal profile is required.
- Retail links stay outside the tools so a commercial destination cannot change the result.
Read before using
These are decision aids, not hands-on product tests, medical guidance, or safety guarantees. Manufacturer specifications can change, personal fit varies, and real-world battery life depends on settings and conditions. Follow the linked source trail and verify the exact model before buying.
Read the full methodology