There are many weather apps that will give you an estimate of the current outside temperature, but they are not always accurate and certainly can't tell you what the current temperature is inside. Modern smartphones may have loads of sensors built in, but a thermometer isn't one of them. But wouldn't that be a cool feature?

Enter Robocat who are working on a thermometer accessory for smartphones that plugs into a standard 3.5mm audio jack. Information is passed into the smartphone via an audio signal, something which must surely rate as one of the most innovative uses of the standard microphone input. Robocat are aiming to offer a range of companion apps for various platforms, but are also creating an SDK so that third party apps can access readings from the Thermodo accessory.

Amusingly the initial push for Theremodo came from a one-star app review for Robocat's own weather app. The reviewer in question complained that the app wasn't providing accurate information when they placed their smartphone next to a fire.

To help raise funds for the development of the accessory Robocat are running a Kickstarter campaign. As with all Kickstarter projects there are a range of backing options to choose from, but if you want to get your own Thermodo sensor, with delivery expected to take place in August, then you're looking at a pledge of $25 (black or white version) or $39 (premium anodized aluminium version).

So how does it work? The projects development team explain:

Thermodo consists of a passive temperature sensor built into a standard 4 pole audio jack enclosed by a sturdy housing. This allows your mobile device to read Thermodo's temperature straight from the audio input. Thermodo sends an audio signal through the temperature sensor. This sensor will then attenuate the signal amplitude depending on the actual temperature. This attenuation can now be detected on the microphone input and through software we calculate the corresponding temperature. Easy peasy! We call this the Thermodo Principle™. Simply plug Thermodo into your device and start the companion app or any other Thermodo enabled apps of your choice. The temperature reading takes place instantly. Thermodo is powered by your device. No external power is required, it can even run in the background while you do important stuff.

What about Windows Phone support? Well, despite originally being envisioned as a product for iOS and Android the developer say that if they receieve sufficient backing ($400,000+ raised) they will also be supporting Windows Phone and will release both a companion app and an SDK. Potentially that means developers will be able to integrate input from Thermodo into their own apps:

At 400K [funding] we're taking the plunge and committing to a Windows Phone Companion App. A lot of people have been asking for Windows Phone support, and if we reach this goal we'll make an app and expand the SDK to better suit Windows phone developers. Like with the Android support, it's something we'll need to hire outside help to get right. It's costly, but it'll be worth it.

The 400K goal looks a little ambitious right now, but there's still a chance it can be met in the time remaining.

Here's a promotional video for the project.