One of the perils of walking around a trade show is that people will walk the isles shovelling random leaflets into your hands as you navigate the show floor. Such was the case with Shadownumber. Much as services like Mailexpire can give you a one time email address, so Shadownumber gives you a temporary extra phone number attached to your existing mobile line.
Neat enough idea although I’m not sure you just shouldn’t be more careful who you give your number to in the first place! If I’m reading it right it’s 30 bucks a month so you’d have to really want it but you can see the details for yourself at www.shadownumber.com