So I received this plant monitor from China recently, and finally had a chance to play with it / tear it down. I would be remiss if I didn't state my disappointment with having to register an email address (un/pw) for usage / access to the iOS app. Suffice it to say but it was a burner address. 
 
More details to come... 
 
Pics: 
 
In the package. 
 
 
It's a little hard to make out, but I see no FCC ID's nor any Bluetooth Sig ID's. 
 
 
Front. 
 
 
Rear. 
 
 
Battery cover removed. 
 
 
Top side of board ... They use a Dialog DA14580 (cortex m0) for BTLE comms. PCB-trace IFA antenna is in upper right quad. Very top is a simple photodiode for light measurement. 
 
 
Bottom side (with battery holder). 
 
 
Closer shot of the Dialog BTLE part. 
 
 
 
Not sure, but I suspect that this is an op-amp. I *think* they use it in the permittivity / dielectric measurement of the water content of the soil. It does NOT appear to be used in the Ion conduction (conductivity) measurement.