From Web of Things blog:
As smart loggers, we use the Sun SPOT Wireless Sensor network on top of which we have built a full RESTful stack. This includes a tiny Web server on the Spot themselves. This Web server offers the functionality of the SPOTs through a RESTful API, partially based on RESTlet a great Java framework for building REST applications. This concretely means for instance that the light sensor of a Sun SPOT can be accessed by browsing to the following URL: http://…/spot1/sensors/light using the GET HTTP verb.
Now, as you all know pretty much everything lately understands HTTP and can access the Web. Thus, building applications on top of this Sun SPOT Smart logger is rather trivial and pretty much looks like a web mashup.