ThermoPro
The ThermoPro TP358: a Bluetooth thermometer and hygrometer that sends the grow room's temperature and humidity to your phone and keeps a history, with the readings on a backlit screen in the room as well.
In StockThermoPro
ThermoPro TP358 Bluetooth Thermo Hygrometer
£17.96
About ThermoPro
Why the TP358
It tells you what happened overnight, which is where most grow room problems start, and it does it for the price of a plain digital hygrometer. The app graphs temperature and humidity over days, so you can see the swing between lights-on and lights-off and fix it.
Where to put it
At canopy height, out of the direct light, halfway into the tent. Other meters are under Hygrometers.