diff --git a/html/style.css b/html/style.css
index 76e5c0e..12049ce 100644
--- a/html/style.css
+++ b/html/style.css
@@ -212,6 +212,7 @@ td {
     border: 1px solid var(--clr-primary-fg);
     padding: var(--size-xs);
     vertical-align: top;
+    white-space: pre-wrap;
 }
 
 th {
diff --git a/luabridge.cc b/luabridge.cc
index 2514f77..33a428b 100644
--- a/luabridge.cc
+++ b/luabridge.cc
@@ -119,6 +119,9 @@ void initLua()
     g_checkers.emplace_back(make_unique<PrometheusChecker>(data));
   });
   
+  g_lua.set_function("external", [&](sol::table data) {
+    g_checkers.emplace_back(make_unique<ExternalChecker>(data));
+  });
 
   g_lua.set_function("smtp", [&](sol::table data) {
     g_checkers.emplace_back(make_unique<SMTPChecker>(data));
diff --git a/manual.md b/manual.md
index d452361..dcc646b 100644
--- a/manual.md
+++ b/manual.md
@@ -92,6 +92,15 @@ dnssoa{domain="berthub.eu", servers= nameservers}
 dnssoa{domain="hubertnet.nl", servers= nameservers}
 ```
 
+## external
+
+Execute some external program, and check whether the output matches a regex and/or a return code:
+
+```lua
+external{cmd="do-thing", regex="success"}
+external{cmd="do-other-thing", rc=0}
+``` 
+
 ## httpredir
 
 Does the http redirect work? TBC. Example:
diff --git a/netmon.cc b/netmon.cc
index 76a6280..4204ef6 100644
--- a/netmon.cc
+++ b/netmon.cc
@@ -531,3 +531,54 @@ CheckResult PINGChecker::perform()
   }
   return ret;
 }
+
+
+// Based on: https://stackoverflow.com/questions/478898/how-do-i-execute-a-command-and-get-the-output-of-the-command-within-c-using-po
+std::pair<int, std::string> exec(const char* cmd) {
+    char buffer[128];
+    std::string result = "";
+    int rc;
+    FILE* pipe = popen(cmd, "r");
+    if (!pipe) return std::pair<int, std::string> (255, "");
+    try {
+        while (fgets(buffer, sizeof buffer, pipe) != NULL) {
+            result += buffer;
+        }
+    } catch (...) {
+        pclose(pipe);
+        throw;
+    }
+    rc = pclose(pipe) / 256;
+    std::pair<int, std::string> ret(rc, result);
+    return ret;
+}
+
+ExternalChecker::ExternalChecker(sol::table data) : Checker(data)
+{
+  checkLuaTable(data, {"cmd"}, {"regex", "rc"});
+  
+  d_cmd = data.get<string>("cmd");
+  d_exp = data.get_or<string>("regex", "");
+  d_rc = data.get_or("rc", -1);
+}
+
+CheckResult ExternalChecker::perform()
+{
+  std::pair<int, std::string> output = exec(d_cmd.c_str());
+
+  d_results.clear();
+  d_results[d_cmd]["rc"] = output.first;
+  d_results[d_cmd]["output"] = output.second;
+
+  if (d_exp != "") {
+    if (!std::regex_search(output.second, std::regex(d_exp))) {
+      return fmt::format("External check \"{}\" against \"{}\" failed, actual output: \"{}\"", d_cmd, d_exp, output.second);
+    }
+  }
+  if (d_rc != -1) {
+    if (output.first != d_rc) {
+      return fmt::format("External check \"{}\" expected rc \"{}\", received: \"{}\"", d_cmd, d_rc, output.first);
+    }
+  }
+  return "";
+}
diff --git a/simplomon.hh b/simplomon.hh
index d6dc6eb..91adf26 100644
--- a/simplomon.hh
+++ b/simplomon.hh
@@ -215,6 +215,24 @@ private:
 };
 
 
+class ExternalChecker : public Checker
+{
+public:
+  ExternalChecker(sol::table data);
+  CheckResult perform() override;
+  std::string getCheckerName() override { return "external"; }
+  std::string getDescription() override
+  {
+    return fmt::format("External check {}", d_cmd);
+  }
+
+private:
+  std::string d_cmd;
+  std::string d_exp;
+  int d_rc;
+};
+
+
 class HTTPSChecker : public Checker
 {
 public: