How to send message to a prim worn by an AV

What is the easiest way to send a message to an object worn by an AV?
The AV may change sims while wearing the object.

Thanks.
Zozo

Bsed on the information you have offered, my first instinct is llEmail. If you have a webserver and the ability to host php, perl, python, asp pages then you can use a combination HTTPRequest->XML-RPC call (HTTPRequest to a php script that forwards data to attachment via RPC call).

If the object will remain within 100m of the sending object (even if it crosses a sim border) then llShout would still be viable

However, I'm not sure you have given us a complete enough description of the issue.

Some questions I have:
1. Who is sending info to the attachment? An object owned by the attachment owner or some other person?
2. Where is the sending object? Is it stationary? Or does it also move, get rezzed and derezzed frequently?
3. Will you need to communicate with the attchment at a high frequency (i.e. every 5 secs) or infrequently (i.e only on request)?
4. Is this an item intended to be sold or distributed widely, or for personal use?

edit to add: I'm not interrogating you. I offer these questions as points to ponder if you feel that none of the suggestions offered by me or anyone are not satisfactory.

I have an attachment which periodically receives email from another prim. To prevent spamming, a script will pause for 20 seconds after sending an email.

Basic code below. (Touch the prim to see its email address.) Use llEmail to send email from a prim.

-peekay

// Check email every this seconds
integer POLL_SECONDS  = 60;

default
{
    touch_start(integer start_num)
    {
        llSay(0, "My email address is: " + (string) llGetKey()
            + "@lsl.secondlife.com");
        llSetTimerEvent(POLL_SECONDS);
    }
    
    timer()
    {
        llGetNextEmail("", "");
    }
        
    email(string time, string address, string subj, string message, integer num_left)
    {        
        llOwnerSay("From: " + address + " [" + subj + "] " + message);
    }  
}

Just to clarify, you do mean an attachment on a different AV than the one wishing to communicate?