Several payment models would fit the aim of this POC, namely, to allow the payment through some crypto asset.
Let's see three of them detailed bellow.
The simplest option. The captive portal performs a direct payment to a private Ethereum address owned by the hotspot handler.
Thanks to the Smart Contract, the hotspot handler is able to put in place the stake schema. The use of the stake schema proves the engagement of the handler, and gives the user the control over the funds transfer termination.
Purchase of dedicated tokens is publicly available. These tokens will be used to pay for Wifi connections at lower prices than in ETH payments. Token option is intended for frequent users looking for longer connections. Therefor, in addition to the stake schema, the user benefits from lower prices in exchange of his loyalti.