One of the (literally) coolest gadgets you can control with your iPhone or iPad has gotten even better.

The iDevice app for the Nest Learning Thermostat, Nest Mobile, has just received a major upgrade. And the new 2.0 version is anchored by the Nest Energy History feature.

As pictured, users can view a summary of exactly how long the heating or cooling system has been on for the last 10 days.

Other features include the ability to see key information, including what the current and target temperatures are, or what the humidity level in the house is. Users can also change the away temperature and pause the auto-schedule or auto-away features.

We first told you about Nest earlier this year at CES. The company behind the technology, Nest Labs, was founded by former Apple Senior Vice President Tony Fadell. While at Apple, Fadell helped oversee the iPod and first three versions of the iPhone.

And Fadell easily transferred his skills used at Apple into designing something that isn’t exactly known as sexy – the thermostat.

In just one week of use, Nest will learn how you use it and adjust accordingly. With a built-in motion sensor, the unit can also detect when you are not at home and adjust the temperature to a preset range.

Nest Mobile is free in the App Store, but it requires having a Nest Learning Thermostat to control. Are you interested in the technology, or does the high $249.99 price turn you off from the product?

I’ve been using the thermostat since late last year and have been consistently impressed. Since I’m in sunny Texas, I haven’t had a chance to realize any energy savings yet. But with the hot summer months coming, I’m interested to see how much my electricity bill shrinks.