Mobile phones are ubiquitous in urban settings across Africa, offering a unique platform for monitoring livestock health. A mixed-methods approach was employed, including surveys, interviews, and data analysis to assess system performance and user satisfaction. Users reported an average increase in milk production by 20% (95% CI: 10-30%) after implementing the monitoring system. The mobile phone-based livestock health monitoring system significantly improved productivity among Nairobi slums farmers, demonstrating its potential for widespread adoption. Further research should explore scalability and cost-effectiveness in different contexts to ensure sustainable implementation. Mobile Phone Monitoring System, Livestock Health, Nairobi Slums Farmers, Productivity Growth The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.