In order to measure the temperature around you using your smartphone, you are going to have to pick up a thermometer add-on. The Thermodo is a cool gizmo that lets you measure the temperature right on your iPhone, iPad, or Android device. It has a temperature sensor built into a standard 4 pole audio jack enclosed by a durable housing. It is plug and play (don’t forget to download the companion app). You can support these guys on Kickstarter.