[echoangle]

I think that was his point. To calculate if you are going to stall in a final, you need to know your weight and flap setting to see if you will exceed the critical angle of attack when doing the turn, exactly because the speed isn’t constant.

[lovecg]

No, you just need an angle of attack sensor. These are increasingly available for small GA planes.

[echoangle]

You need an AoA sensor to see if you are currently stalling or are just about to stall. To predict if you will stall at a specific point in your approach before you’re there, you need to know your weight, too.

[blt]

stall AoA depends on flaps though?

[lovecg]

Yes, and some sensors do take flaps position into account (or you compromise and have it display the AoA with a typical approach setting).