This one accepts messages on local chat based on a touch trigger. It also requires the n2k script in the same primitive.

failednoob_online_detector.lsl

///////////////////////////////////////////////////////////////////////////
//  Copyright (C) Wizardry and Steamworks 2011 - License: GNU GPLv3      //
//  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  //
//  rights of fair usage, the disclaimer and warranty conditions.        //
///////////////////////////////////////////////////////////////////////////
 
key _kReq = NULL_KEY;
string _kName = "";
key _kKey = NULL_KEY;
 
default
{
    state_entry() {
        llSetText(_kName = "Touch me to look for an agent's status.", <1,1,1>, 1);
    }
    touch_start(integer num) {
        llListen(0, "", llDetectedKey(0), "");
        llSetText("Type the name of the agent in local chat.", <1,1,1>, 1);
    }
    listen(integer channel, string name, key id, string message) {
        llSetText("Checking...", <1,1,1>, 1);
        _kName = message;
        llMessageLinked(LINK_THIS, 0, _kName, "");
        llSetTimerEvent(10);
    }
    timer() {
        llSetTimerEvent(0);
        if(_kReq == NULL_KEY) {
            _kReq = "a";
            llSetText("Agent could not be found.", <1,1,1>, 1);
            llSetTimerEvent(5);
            return;
        }
        llResetScript();
    }
    link_message(integer sender, integer num, string str, key id) {
        if(str == "KN2K") if(id) {
            _kKey = (key)id;
            state check;
            return;
        }
    }
    changed(integer change) {
        if(change & CHANGED_INVENTORY) llResetScript();
    }
 
}
 
state check 
{
    state_entry() {
        _kReq = llRequestAgentData(_kKey, DATA_ONLINE);
        llSetTimerEvent(10);
    }
    timer() {
        llSetTimerEvent(0);
        llSetText("Agent could not be found.", <1,1,1>, 1);
        llResetScript();
    }
    dataserver(key id, string data) {
        if(id != _kReq) return;
        if(data == "1") {
            llSetText(_kName + " is online.", <0,1,0>, 1);
            return;
        }
        llSetText(_kName + " is offline.", <1,0,0>, 1);
    }
    touch_start(integer num) {
        state default;
    }
 
}