BSX Insight (Starts at ~$299)
If you are an endurance athlete, you need more out of your wearable fitness tracker. You want to know when to conserve energy so that you can finish strong in a race, and one of the measurements that can help you achieve this is lactate threshold. Previously available only as an expensive blood test, it can now be measured right on the course by the BSX Insight sensor (along with other pace, cadence, heart rate and calories).
The sensor attaches to your calf and syncs to your sports watch or smartphone. After your workout or event, you can access your stats on the web. The company is currently taking preorders for running, cycling and multi-sport versions.
For more information and to pre-order, check out https://www.bsxinsight.com.