Product review (5 stars): Job or health requires knowing temperature and humidity?  This is a simple and low-cost solution.
This does exactly what it says it will do.  Download an app for your Android (which is what I tested it on) or iPhone, and plug the device into your headphone jack, and you can view and capture the temperature and humidity in real time.  The software (which is simple, but not quite as intuitive as it could be) allows you to create multiple different locations, and you can retain a list of readings for each of those locations.

If you're in a profession that requires careful tracking and understanding of temperature and humidity in different areas - or if you are interested in tracking this information for health reasons, this is a great little device.

A few items to note:
* This is the size and shape of a USB memory stick.  The lid snaps on over the headphone connector.  Very small and easy to take with you.
* To my knowledge, the device will only have power and capture readings when connected to your mobile device.  So you can't leave it somewhere for a day and then come to see what the readings were while you were gone - you have to be physically present and click the button to capture a reading on your phone in order to capture.