Sensors for Amazon Dash Replenishment

And yet more.  This points out that the idea goes beyond the push button for replenishment idea.  It also includes sensor based product replenishment:

" .. Dash Replenishment Service can be integrated with devices in two ways. Device makers can either build a physical button into their hardware to reorder consumables or they can measure consumable usage so that reordering happens automatically.

For example, an automatic pet food dispenser made with built-in sensors can measure the amount of pet food remaining in its container and place an order before running out. Device makers can start using DRS with as few as 10 lines of code. .. "