The RPTool on Second Life is a roleplay communication device designed to allow avatars to talk, emote, whisper and shout under their character names.
It works by sending the message to a preset chat channel, which is intercepted by the tool and forwarded, changing the displayed speaker name.
It can be obtained for free here, with a premium more developed version also available here.
RPTool is commonly used in the Final Fantasy VII and Star Wars RP communities.