We present DDMon, a proof-of-concept monitoring tool for distributed black-box deadlock detection in Erlang and Elixir systems based on generic servers (gen_server). DDMon acts as a drop-in replacement for the gen_server module, with minimal user intervention required. When activated, DDMon deploys an invisible monitor alongside each gen_server process; the monitors communicate with each other to detect deadlocks, without introducing centralised bottlenecks. In case of a deadlock, DDMon reports the exact set of deadlocked processes without false positives or false negatives: i.e., DDMon only reports real deadlocks, and if some processes become deadlocked, DDMon will report them. DDMon is the implementation and companion artifact of our work accepted at OOPSLA 2025: “Correct Black-Box Monitors for Distributed Deadlock Detection: Formalisation and Implementation”.