Current market research indicates high future demand for broadcast services such as Mobile TV. While underlying competing bearer technologies are being extensively tested and refined, the focus keeps shifting towards interactive services on top of mobile broadcast. In order to investigate the possibilities of interactive mobile TV, projects require testbeds for convergent architectures and services. However, related technologies and standards still need to mature and key components such as open, programmable TV-enabled phones are still missing. In this paper, we present our testbed for mobile interactive TV for early stage technology and application prototyping, with a focus on mobile client and network aspects. Furthermore, we illustrate the utilization of the system and outline selected future development issues concerning mobile interactivity options.