Yes we already have a working platform.  If you want to know how selling or buying IoT sensor data would work on Databroker, check out the BETA version of the platform: https://beta.databrokerdao.com/

The data flows from the sensor to the gateway operator. Like a telco for example. The gateway operator runs the dAPI on their end (so every gateway operator runs their copy of the dAPI and their blockchain node). Secondly, the marketplace records who owns what at what time in the smart contracts. When you buy access, you also specify a target where it needs to go, e.g. your AWS S3 bucket. Now every time data comes into the gateway operator, it will pass it to the dAPI that will check who has bought access to it. it will then send the data onwards to the location specified in the purchase. The gateway operator takes a percentage of the sale to cover the server and network costs to do so.
so as a buyer, you pay DTX tokens and add a target location, and the data will appear there.
The data itself does not flow over the blockchain network, the scale would be impossible.