Chrome: In the workplace, emails and chatrooms are often stored permanently, which isn't helpful if you want to ask a colleague if they really had a sick day or not. O.T.R. (Off The Record) is a Chrome extension that creates non-permanent conversations, with messages vanishing after you read them.
Signing up only requires an email address (you can also sign in via Yammer if you use that). You can send photos as well as basic text messages.
As with similar consumer applications (Snapchat springs to mind), you can't stop someone else screen grabbing a specific message. However, for casual chat, this is an interesting idea. It's currently only available for Chrome, though Firefox, IE and Safari versions are in the works.
The obvious downside? The biggest challenge with workplace chatrooms and other collaboration tools is getting people to engage with them. Having an additional distraction won't help with that.