  Proliferation of ubiquitous mobile devices makes location based services
prevalent. Mobile users are able to volunteer as providers of specific services
and in the meanwhile to search these services. For example, drivers may be
interested in tracking available nearby users who are willing to help with
motor repair or are willing to provide travel directions or first aid. With the
diffusion of mobile users, it is necessary to provide scalable means of
enabling such users to connect with other nearby users so that they can help
each other with specific services. Motivated by these observations, we design
and implement a general location based system HelPal for mobile users to
provide and enjoy instant service, which is called mobile crowd service. In
this demo, we introduce a mobile crowd service system featured with several
novel techniques. We sketch the system architecture and illustrate scenarios
via several cases. Demonstration shows the user-friendly search interface for
users to conveniently find skilled and qualified nearby service providers.
