The move turns LocustWorld's mesh boxes, which link together to form a wireless network, into Voice over IP (VoIP) switches. This means that people who use a wireless network that runs on LocustWorld's mesh software will be able to make voice calls over the Internet, rather than using their existing landline.
Everyone connected to the same mesh will be able to call each other for free using VoIP. They will also be able to use the same telephone number regardless of where on the mesh they are connected.
SIP was introduced by the Internet Engineering Task Force (IETF) as a way of simplifying the process of running VoIP connections across the Internet. Networks running SIP can handle VoIP calls regardless of which vendor created the handsets or soft phones.
"Being able to support SIP routing within the LocustWorld mesh adds a new dimension of utility to the network, allowing users to utilise industry standard IP telephony services over a wide coverage area. The mesh network can now also be a large scale wireless phone network," said LocustWorld's Jon Anderson.
Supporters of SIP say that it will let service providers transform their traditional revenue streams by offering IP-based services that combine elements such as telephony, email, instant messaging, and video streaming.
According to LocustWorld, there are now plenty of affordable SIP phones, both hardware and software, on the market, with more large telcos offering gateways between SIP and their PSTN networks.
LocustWorld first hit the headlines in 2003 after Anderson wrote a piece of software called the MeshAP that configures a group of wireless access points into a coherent mesh where data is passed from node to node until it reaches its destination.
MeshAP is freely available to download from the LocustWorld site. The company also sells meshboxes; small fanless PCs that run the MeshAP software and act as nodes on the mesh.
These meshboxes are now being deployed worldwide, from Scotland and Yorkshire to the Washington State and the Gulf Coast of Florida, LocustWorld says. In many cases, community activists are using them to bring high-speed connectivity to areas where ADSL and cable broadband aren't available.
Click here to read more about SIP.
ZDNet UK's Jonathan Bennett contributed to this report.