Ceric, I tested this out after installation while backing up at tree and concrete pillar and cardboard box, and the sensor did pick up the objects and beeped as a normal system.
I have not tested on human so this I will try it out today and let you know if this does work if there are people...
I have installed after market backup (reverse) sensor on 2011 CX9
I have installed after market backup (reverse) sensor on 2011 CX9 - all instructions and very easy.
I bought my CX9 Jan 2012 and it is Sports model so not the top of the line and so it did not come with the back-up (reverse)...