• Muscle-inspired anisotropic aramid nanofibers thermoelectric aerogel was prepared via directional freeze-drying strategy.
• Resultant anisotropic aerogel exhibited high-efficiency thermoelectric conversion with Seebeck coefficient of 46.78 μV K−1 and low thermal conductivity of 0.048 W m−1 K−1.
• Thermoelectric aerogel-based multistage wireless high-temperature alarm system achieves a wide temperature sensing range (50–400 °C) and sensitivity response time (trigger time ~1.43 s) for firefighting clothing.
• The anisotropic aerogel integrates thermal barrier and self-actuated temperature monitoring, offering proactive safety for firefighters under extreme conditions.