Given a FritzBox at the IP 192.168.179.1 with captive portal enabled, the following script accepts the policies of the site and access to the internet should be possible. /system script add name=fritz-captive source="/tool fetch \"http://192.168.179.1:8186/trustme.lua\\\?accept=yes\" output=user"
I use MikroTik Routerborads quite a lot on remote sites to establish a secure tunnel to connect to internal services remotely (for example for employee time clocks). I like using OpenVPN because it is simple to configure and supports both, L2 (tap) and L3 (tun) secure (encrypted) tunnels. MikroTik’s Routerboards on the other hand are quite cheap and are providing a neat “black box” appliance which can easily handed to people with no IT experience.