Thanks for the offer to help with an app. If I get to that point, you'll know
The data is all cached during a run, and only written to the card after a button press. Same approach would be used with Bluetooth. The *highly* variable latency of writing to SD cards drove me to use a cached data model. Even with the additional stuff I might add in the future, there's room for over 20 mins of data at 150Hz.
As it stands, and it's not optimised in any way, a single cycle of data capture is well under 2ms, so it would be possible to up sampling to close to 500Hz and maybe beyond for specific use cases.
Probably not much point increasing the sampling rate unless the sensors are rated at providing data updates at that rate.
Would it be viable to periodically flush the cached data to the microSD card?