I have just purchased a T300 and connected it via the H200 hub and it works very well.  

I notice that one of the pairs of moisture sensors on the underneath are tapped with female threads;

this would seem to indicate that external sensors can be connected to these

however I have been unable to find any such accessory on the TP Link website.

Can you confirm if this is available now, or if not when is it likely to be made available?

Thanks

Roger