I would like to see real-time data (speed and cadence, no heart-rate for now) on Strava Live on my iPhone 7. Do I need to install bluetooth sensors on my bike or it just magically works? If it just works, is it reliable/accurate or I should still install sensors and let it get this information from the bluetooth sensors?

  • To be honest - bluetooth is the wrong protocol for sensors. ANT+ is far more economic on battery and works fine. Bluetooth sensors use batteries 10 times quicker than the same ANT+ sensor, even BLE ones. But iphones are only bluetooth- to get ANT+ you need an adapter, or a Wahoo RFLKT, a garmin, or an android phone which do ANT+ natively. Comment because not an answer.
    – Criggie
    Apr 11 '17 at 1:04

Strava (Premium) can determine your speed using GPS data, although GPS can be less accurate than a dedicated sensor because it jumps around a bit.

There's no magic way to determine cadence without a sensor, except maybe counting it in your head.

  • In the case of a fixed gear bike, you can determine cadence from speed and gearing information. So, you could in principle calculate it from the GPS data.
    – Batman
    Apr 10 '17 at 16:03
  • You may want to add a note that without a "STRAVA PREMIUM" subscription, you only see average speed / cadence data for your ride. If you want instantaneous real-time data, you got to pony up. :-(
    – RoboKaren
    Apr 10 '17 at 16:32
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    iPhone has accelerometer, so it might be possible to help speed measurements using the data. If you keep the phone in pocket, it could be even possible to extract cadence from the data.
    – ojs
    Apr 10 '17 at 18:27
  • That's a good point about the accelerometer. I'm not sure how well it would measure speed, since your acceleration is the same at a constant 5kph as at 25kph, you'd have to keep a running sum of all accelerations which sounds very error prone. Cadence is a good point, somehow an iphone by default measures your steps, but at that point the phone becomes the sensor. And since you can't see the screen, you couldn't see the live data anyway. And of course as far as I know Strava currently does neither of these (it does use the barometer for elevation though).
    – Jamie A
    Apr 10 '17 at 19:16

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