First version of this LSL script. Tested in OpenSimulator.

query.lsl

@@ -0,0 +1,52 @@
+string queryRequestURL = "[Insert your full URL here]";
+integer listener = 0;
+integer CHAT_CHANNEL = 5;
+key http_request_id;
+key avatar;
+
+default
+{
+    state_entry()
+    {
+        llSetText("Touch to get an avatar UUID from Second Life®", <1,1,1>, 1);
+    }
+    
+    touch_start(integer howmany)
+    {
+        if (listener == 0)
+        {
+            avatar = llDetectedKey(0);
+            listener = llListen(CHAT_CHANNEL, "", avatar, "");
+            llSetText("In use by " + llDetectedName(0), <1,1,1>,1);
+            llWhisper(0, "Say an avatar name in chat prefixing it with /" + (string)CHAT_CHANNEL + "; touch to reset");
+            llSetTimerEvent(360.0);
+        }
+        else if (avatar == llDetectedKey(0))
+        {
+            llResetScript();
+        }
+        else
+            llWhisper(0, "In use");
+    }
+    
+    timer()
+    {
+        llResetScript();
+    }
+
+    listen(integer channel, string name, key id, string message)
+    {
+        http_request_id = llHTTPRequest(queryRequestURL + "?name=" + llEscapeURL(message), [], "");
+    }
+
+    http_response(key request_id, integer status, list metadata, string body)
+    {
+        if (request_id == http_request_id)
+        {
+            if (status == 200)
+                llInstantMessage(avatar, "Key is " + body);
+            else
+                llInstantMessage(avatar, "Error " + (string)status + ": " + body);
+        }
+    }
+}