Riker

Track your strength with Riker. Riker lets you track your reps during your strength training workouts. Search or drill-down to find your movement and variant (e.g., bench press with dumbbells), and simply enter the weight used and the number of reps. You can also indicate if you went to failure or not.
Riker will also keep track of your rest time spent between sets automatically.
In addition to tracking your sets, Riker lets you track relevant body measurements, including your arm size, chest size, calf size and more.
Plenty of charts are provided to track your progress. Riker provides charts to track your weight lifted over time, your rep count over time and your time spent between sets over time. Pie charts are provided to give you an aggregate view of these metrics.
Riker's Apple Watch app allows you to input your sets and body measurements with ease.
Riker integrates with Apple's Health app. The sets you record are saved as strength training workouts in Apple Health. Any body weight measurements you record in Riker will also be saved in Apple's Health app.
Forget to bring your iPhone to the gym? Riker's Apple Watch app works just fine untethered from your iPhone enabling it to work perfectly when your iPhone is unreachable. Riker will save your sets and body measurement logs locally to your Apple Watch, and later you can bulk-sync them to your iPhone.
Want to import your Riker data into your favorite spreadsheet program? Riker has an export function to extract your sets and body measurement log data to CSV files. There's also an import function so you can restore your data to a new device. It's your data. You'll always be in full control of your data with Riker.