Remember invisible ink -- one of those utterly pointless products they marketed to kids so they could pass notes without getting caught? If you miss the good 'ol days, gossiping with Mary Alice in the back of English class using your super-secret decoder pen, fret not -- there's now a modern-day version just for grown-ups.

Introducing Kameraflage! If you're interested in the science of how this works, go here -- but the point is: the technology uses colors that are invisible to humans, but that are picked up by digital cameras. So, you can add a little surprise to your t-shirt that won't show up until someone takes your picture.

Of course, whatever you put on there will be seen by anyone who takes your photo -- not just your BFF -- so be careful what you "hide."