I recently received my Red Pitaya which I had funded as a Kickstarter project. The Red Pitaya is a small (“credit card size”) measurement equipment developed in an open source project (both HW and SW are open source). It is actually quite a versatile device as both the HW and SW  can be easily modified (you could call it reconfigurable instrumentation). For full details please take a look at the Red Pitaya official web site:

http://redpitaya.com/