These days fitness trackers tend to multi-task as standard. The likes of the Fitbit Alta HR and the upcoming Gear Fit 2 Pro offer everything from sleep monitoring to calorie-counting -- with Samsung's wearable also reportedly boasting swim tracking. But, all those features can prove a turn-off for buyers looking to hone in on one specific task. If, for example, you just want to focus on your heart rate, why would you fork out $150 for a bunch of tricks you don't need? That's where Polar's new OH1 optical heart rate sensor comes in. The $79.95 wearable trims out the fat to focus on your ticker, and little else. And (seeing as Polar's been making top-notch activity trackers for years) you can probably bet it does that well.