Meet Thermodo: A Tiny External Thermometer That Lives In Your iPhone’s Headphone Jack

Danish startup Robocat has built a lot of software for Apple’s iOS devices, but today the company is branching out with the launch of a new hardware accessory for the iPhone, iPad, and Android devices. It’s called Thermodo, and it’s a very small hardware thermometer that fits in your device’s headphone jack, and transmits real temperature data for use in apps.

The Thermodo hardware has a passive temperature sensor, housed in an audio jack and protected by a small cylindrical end cap that only extends around a quarter of an inch out from your device. It doesn’t need its own power source, and it transmits weather data as an audio signal that can be picked up by your phone and translated into the corresponding temperature on your phone via an API, which the company will first use in a dedicated Thermodo companion app for iOS, as well as in two of its previously released apps, Haze and Thermo.

The Thermodo works offline, indoors and out, and comes with a carrying case keyring to make sure you don’t lose the tiny thing when it’s not in use. Robocat says that eventually, any device could potentially support Thermodo, including Raspberry Pi, Macs, and Arduino-based gadgets, thanks to the company’s open source SDK.

I talked to Robocat founder Willi Wu about the project, and why it came to be in the first place. He says the company branched out from its core focus on mobile weather apps based on feedback from users.

“The idea Thermodo is actually based on an indirect request from our users,” he explained.” We received several one star reviews because our users wanted the feature of measuring the temperature themselves right where they are. Currently the iPhone does not support any access to any temperature reading within the phone nor is there a dedicated sensor for this purpose. We wanted to attack to this problem anyway and came up with the most simple solution we could imagine, Thermodo.”

While other devices like the Square credit card reader and the Jawbone UP fitness band use the headphone jack as a way for accessories to communicate with smartphone devices, Wu says that Thermodo is fundamentally different in its approach. That opens up plenty more possibilities for how the company could use the tech in the future to create other kinds of sensors, he says.

“Thermodo is not translating sounds to data like Square or other softmodem-based products,” he said. “It turns out that we can apply this method to all kind of applications. What we do is converting the temperature into an electrical impedance and this impedance is determined by what we call the “Thermodo Principle.” Now we can convert all kind of things into an electrical impedance, like for example wind speed, pressure, brightness and so on.”

Wu says Robocat’s technical lead is already measuring his resistors and capacitors in this manner, and that the company is experimenting with some of these alternate sensing capabilities already. Eventually  Thermodo could have a number of sibling devices to gauge just about everything under the sun (including the sun’s brightness).

Thermodo is looking for just $35,000 in funding, and pre-order pledges start at just $19 for a single Thermodo unit. This is a project that will hit its goal quickly, and I can’t wait to see what comes next from Robocat’s new hardware focus.