**5. Conclusions**

Employing a participatory approach, we developed an m-health campaign to improve knowledge about second hand smoke in socially disadvantaged families. The campaign is ready to be disseminated in social networks, ideally by trustworthy persons such as doctors. Moreover, a follow-up study should evaluate the effectiveness of the campaign.

**Supplementary Materials:** The following is available online at http://www.mdpi.com/1660-4601/15/9/1945/s1, Supplement S1: List of all items used in the online survey.

**Author Contributions:** K.R., T.W., V.K. and D.N. planned and designed the study. F.S., J.G., S.B. and T.W. coordinated the field phase. F.S. and V.K. conducted the qualitative data analysis while S.B., K.R. and T.W. performed the quantitative analyses. The manuscript was drafted by K.R. and T.W. with contributions from all authors. All authors read and approved the final manuscript.

**Funding:** This research was funded by the German Federal Ministry of Health under gran<sup>t</sup> number "Kapitel 15 02 Titel 684 69".

**Acknowledgments:** We cordially thank all participants, the collaborators and the field workers for their support.

**Conflicts of Interest:** DN is a delegate in the Aktionsbündnis Nichtrauchen (ABNR, Action for non-smoking) and is a member of a pharmaceutical (Pfizer) Advisory Board on Vareniclin. The other authors declare no conflicts of interest.
