Social Intelligence Lab researcher Michael Khalemsky will be presenting a simulation modeling tool to analyze EMS vs. smartphone-based samaritan response, at the INFORMS session on Healthcare Analytics and Medical Decision Making. Smartphones and location-based social networking technologies present an opportunity to re-engineer certain aspects of emergency medical response by establishing Emergency Response Communities (ERC). The ERC Effectiveness Modeler (ERCEM) estimates the efficacy of smartphone-based samaritan response for given medical condition and geographic region. The ERCEM uses parameters such as population density, prescription adherence, smartphones penetration etc. and performs Monte Carlo simulation to compare potential ERC response to traditional EMS response. We present the modeler and show how it assessed effectiveness of ERC for anaphylaxis in the USA based on data from the NEMSIS project.