The trend towards smart factories necessitates protocols for wireless transmission of production process information. Protocols must transfer process information timely even with temporary wireless interference on the factory floor and regardless of machines' location in the network topology. TANDEM is a topology-independent wireless multi-hop network protocol that implements in-network prioritization to provide a useful, early approximation of process information. Tailored to often required time series data transmission, TANDEM applies a time-frequency transformation to prioritize more valuable information parts, decouples multi-hop communication steps to improve robustness, and uses a periodic acknowledgment overhearing mechanism to save transmissions. We analytically discuss reliability and fairness aspects and show using simulations that TANDEM's prioritization is beneficial to obtain an early preview of sensor information even in large factories. In addition, we implement TANDEM on industrial grade hardware and provide a performance evaluation.