Today’s smartphones offer countless apps to check the weather, find out upcoming forecasts, or even get alerts when it’s about to rain or snow. But no app can tell you exactly what the temperature is right where you stand. That’s why Robocat, the developers of Haze and other smartphone weather apps, created Thermodo, a small device that plugs into the headphone jack of your Android or iPhone.

Thanks to a highly-sensitive sensor inside of its minuscule housing, Thermodo can tell you the exact air temperature wherever you are, whether that’s at the top of a ski slope or sweating away in the sauna afterwards. It works with an accompanying app to show instant readings and if the temperature is climbing or falling. The Thermodo is available in two versions: a basic model in black, red, or silver that sells for $29.99, and a premium version for $44.99 that offers a brushed aluminum finish with engraved logos. Both have the same temperature reading capabilities, though, so you’re really just paying more for aesthetics with the premium model. Robocat also ships the Thermodo with a matching keyring to house the unit when its not in use.

Instant temperature readings right on your smartphone

I tested the Thermodo with an iPhone 5S, Moto X, and new HTC One and found that it did live up to its promise: it was able to tell me the air temperature in my environment and track it as the temp rose or fell. The Thermodo would almost instantly react to changes in environment, such as when I walked outside or stuck my phone in the freezer. But its ultra-high sensitivity proved to be quite difficult to deal with when trying to get an accurate reading. Simply touching the unit would cause it to read a different temperature as it sensed my body heat, and the smartphone’s own heat would impact the reading significantly, as well. The app does have some basic adjustments to compensate for device heat, but if you’re looking to get a truly exact reading, it’s best to use an audio extension cable.

It would be great if the Thermodo could read more than just temperature

It’s fun to see exact temps as they change, and the Thermodo quickly reminded me that despite what the calendar says, the Northeast still hasn’t left the cold grip of winter (at this point, I’m not sure it ever will). It can also prove useful when testing a freezer, heater, or other temperature dependent appliance. But for the most part, it’s a novelty, a way to win a bet with your friends or prove to your significant other that it’s not nearly as cold in the house as they claim and there’s no need to turn the heat up. It would be great if the Thermodo did more than just read temps, such as sensing humidity or barometric pressure, something many smartphones already do today.

For basic temperature readings, however, the Thermodo does the job and is worth the $30 price tag (I’d save my $15 and go with the basic model). But I’ll be sticking with my assortment of weather apps for now, which provide me with forecasts, alerts, maps, and other necessities when checking the weather.