Mobility in urban environments is often coupled with a quest for efficiencies such as a nearby parking spot, a ride to some destination, a date for dinner, a ticket to the theater, or any other kind of service that one might need while on the move. The idea is an ad hoc, mobile "Craig's List." We demonstrate a system that provides an easy way to advertise services or goods offered or sought by means of mobile phones and ultra-mobile PCs, and we are concerned with issues of ensuring trust, security, and anonymity for all participants.