This sensor is relatively complex to set up, but it works with older Arduino boards like the first-gen Uno. Measuring the pH ... in mind that nothing will beat a proper professionally built ...

You may be interested in a project published to the Hackster.io website earlier this year providing instructions on how to create a simple wearable heart rate monitor using an Arduino Nano R3.

And the Touch Board from Bare Conductive wants you to combine your DIY spirit with the ability to turn practically any surface into a sensor. At the heart is an Arduino compatible microcontroller ...