Difficult to tell from that angle - but from another angle I found it looks like there's a small window on the front facing towards the front tyre - between 3 and 6 o'clock on the front - though it could be a shadow!?
https://www.motorsport.com/f1/photo/mai ... 1110&i=149
I would assume tyre temperature sensor.
That said Sauber looked like they were running those in the wing mirrors... could be a more powerful antennae for data logging?
Mercedes were running something similar on the same camera mount on Hamilton's car in FP1 (though it looked more like a conventional FIA/FOM camera only longer so maybe that was your 3-d camera??).
Only real answer is that it's impossible to know.