You simply wear the device and when someone asks you if you want to be bitten or such you decline their offer. Then you just type /offer blood to (insert name) or /give blood to (insert name) and they get a message. It will say in chat... (your name) has offered to give you blood .. click yes to accept. They will receive a blue pop up menu that will allow them to accept, decline, or mute. Just like you get when they ask you if they can bite you. Remember they can always just press decline which is one thing they keep saying you can do when they ask to bite them

Remember this item is totally free, and is not to be used as a griefer tool. Altho I don't know how it could be considered a griefing tool or spamming tool since there are so many similar items out there that ask people to accept, decline, or mute and all are unsolicited usually.
Here is the SLurl to get your own for FREE. That means you pay nothing now and you pay nothing later and your still just as cool as when you bought it.
http://slurl.com/secondlife/Marrowstone%20Island/144/229/51