250+ iOS apps curated and reviewed
Whether you're new to 4x4 hiit or looking for an upgrade, our curated collection of 250+ iOS apps has something for everyone. Each app is reviewed and rated by real users, helping you make an informed decision.
| # | App | Price | Rating | Ads | In-App Purchases | Updated | |
|---|---|---|---|---|---|---|---|
| 1 |  | Free | — | No | No | May 2026 | |
| 2 |  | Free | — | Yes | Yes | Jul 2026 | |
| 3 |  | Free | 5.0★ (2) | No | No | May 2026 | |
| 4 |  | $9.99 | 1.0★ (1) | No | No | Jul 2026 | |
| 5 |  | Free | — | Yes | Yes | Sep 2026 | |
| 6 |  | Free | 5.0★ (3) | No | Yes | Sep 2026 | |
| 7 |  | Free | — | No | No | Sep 2026 | |
| 8 |  | Free | — | Yes | Yes | May 2026 |
This app guides you through High Intensity Interval Training (HIIT) workouts using your heart rate as a guide. It sequences exercise between high and low intensity intervals, displaying your progress on a speedometer-style dial. Warning chimes alert you if your heart rate falls outside the target zone.
