Here is a compact device that lets you monitor your environment wirelessly. It is a Bluetooth smart thermometer, hygrometer, and pressure sensor. The device is compatible with iOS and Android devices. The Tempo can be calibrated with accuracies of +/- 0.3 Celsius for temperature, 5% RH for humidity and 2 hPa for pressure.
The device has a range of up to 50 feet indoors. It is powered by 2 AA batteries. You can get yours for under $50 at this time.