Abstract Users require appli ations and servi es to be available everywhere, enabling users to fo us on what is important to them. Therefore,

ontext information from users (e.g., spatial data, preferen es, available on-

ne tivity, and devi es, et .) needs to be a essible to systems that deliver

servi es via a heterogeneous infrastru ture. We present a novel approa h to

support ubiquitous sensing and availability of ontext to servi es and appli a-

tions. This approa h oers a s alable, distributed storage of ontext derived

from sensor networks wirelessly atta hed to mobile phones and other devi es.

The support handles frequent updates of sensor information and is interop-

erable with presen e servi es in 3G mobile systems, thus enabling ubiquitous

sensing appli ations. We demonstrate these on epts and the prin iple opera-

tion in a sample ubiquitous mobile awareness servi e. The importan e of this

ontribution, in omparison to earlier work, lies in the availability of real-time

ubiquitous sensing to both appli ations on the Internet as well as appli ations

in mobile systems.