Do you have feel for what input sample rate could be pushed over BLE ? I have played with Measurement Computing’s example Android apps for their Bluetooth ADC box that we own, and frequency response is not too bad. But we’re looking at portable/wearable applications and their box is quite big.
I guess to some extent I am trying to get your device to do something it wasn’t designed to do – I know it’s a multimeter not an oscilloscope ! But the presence of the graph makes me think ‘oscilloscope’. ;)
Is it at all possible that you could implement lower sample rates (eg 10hz) on the meter side and a 1-sample buffer (ie actually no longer a ‘buffer’), so basically data was then being sent over BLE every 0.1 sec, or whatever it can handle ? And the app just plots whatever it receives and can keep up with ?