Amazon Dash is a silly way to re-order various products from Amazon. That said, if you like the idea of it and prefer more control, DIY enthusiast Denis Papathanasiou shows you how to build your own with a Raspberry Pi.
Papathanasiou's version gives you a lot more control over what you order and how much you pay. Essentially, you hook a Pi up to a scanner and scan items you want to order. It works with any product and you can say no to an order if it's priced too high. Basically, it's an Amazon Dash that's actually useful. You can find the guide and software to make it for yourself over on Papathanasiou's site below.
PiScan: an open-source version of the Amazon Dash Button using a Raspberry Pi [Denis Papathanasious]