how to connect an embedded device to wifi network that needs validation

in hotel or public wifi hotspot places, it's often necessary to validate oneself in a web browser that you've got proper credentials as guest and agree to agreement.

for embedded device (i.e. media box running stripped-down linux) that doesn't equipped with a full fledged web browser, how to connect to the host network?

On occasion I believe I've seen http command line sequences to get able to grab a file, similar to wget, but using http. I wonder if you would be prompted if you tried some sort of http from the command line. The only other option I could see is to use something else small like a Pi and have that be capable of running the full browser and then act as a gateway for your embedded device, but I'd then plug into the Pi's wired Ethernet with my embedded device, if I had that connection available.