You need a gateway more or less since the devices don't use the same physical means of communication as the other ones on the network. The mesh network devices

You need a gateway more or less since the devices don't use the same physical means of communication as the other ones on the network. The mesh network devices in this post use a 802.15.4-compatible radio, which doesn't work with wi-fi on a physical layer, so the gateway translates this (and IPv4 <-> IPv6). All RF communication is regulated (broadly speaking). On the relevant freq. bands here, the ISM bands on 868/915 and 2.4 GHz, the bands are unlicensed (you don't need a license) but you have to comply with certain rules. You must not send too strong, or too much, or occupy too wide freq. band. You must be able to cope with other transmitters. Re phones and connections, I think what you mean is ad hoc mesh networks using the wi-fi that the phones (and laptops) have built in. Then you get a network in which the devices can communicate with each other (share files, messages,etc), where they otherwise might have required internet to reach eachother. It's a different (but interesting) thing...