Amazon now have their Dash button that allows you to buy a restricted range of goods from, surprise - Amazon - when something runs out. So you put the button on your washing machine, press it when the powder gets low, the button automatically does a buy-with-one-click using your home wifi, and a new pack arrives a day later.
But you can't set the buttons up to buy anything you like from Amazon, let alone from other suppliers. The button locks you in to products that may well not be the best deal, nor exactly what you want.
Clearly what's needed is a user-programmable button that you can set up to take any online action that you preset into it. Thus pressing the button might indeed do an Amazon one-click, or it might add an item to your Tesco online order, or it might boost your web-controlled central heating in the room where you are sitting, or it might just tweet that you are having your breakfast (if you feel that the world needs to know that on a daily basis).
Electronically, such a device would be straightforward. And - as a marketing opportunity - it is potentially huge. It would allow people total control over what they buy and from whom, completely subsuming Amazon Dash within itself among a much wider range of possibilities. And in addition it could be used to carry out a vast range of non-buying online actions that are amenable to your pressing a button when you feel like it.
If I can find a spare afternoon, I might just design it and open-source the results...