Vodafone (Portugal) lets cell phone subscribers pay for hotspot access via SMS: Vodafone has launched its WirelessLAN service in several locations around Portugal, and allows users to pay for a session by sending an SMS message requesting access. The service will cost 5 euros an hour, 12 euros a day, or 30 euros for 72 hours, but will be limited to the cost of a single SMS message per session until the end of the year to promote the service.
Apparently, any roaming partner of Vodafone's cell networks, which they count as 281 operators in 134 countries, can use SMS within Portugal to pay for service, too.
This service is similar to Excilan's in its interesting crossover between cellular telephone billing and an out-of-band authorization. In Excilan's method, you enter your cell phone number in a gateway page on your Wi-Fi equipped laptop or handheld, and then you are called by an automated service to approve the session. Excilan has arrangement with just a few WISPs and cell operators.