should also work

I am sorry but I am unable to answer the question, I have no terms of comparison.

Extract from the H9 product description:
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"In addition, you can use the compatible 5 kHz technology to send the measurement data to compatible fitness devices such as training computers for ergometers etc."
So it should work.
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Perhaps another important detail .
You can only connect the H9 sensor to one device.
So either the stepper or the fitness watch / app.
If you want to connect both, it is better to use the H10 belt. It can connect to 2 devices at the same time.

Extract from the H10 product description:
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Connect your Polar H10 to an ANT+ compatible fitness device, bike computer or other training device.
ANT+ and Bluetooth connections can be active at the same time.
Thanks to Bluetooth and ANT+, you can connect a wide variety of devices - even several at the same time.
Polar H10 is fully waterproof and transmits heart rate data (when swimming) via 5 kHz transmission.

Hello,
unfortunately I can't answer that question!