TextSpy claims to be able to retrieve the last 10-20 deleted messages from your SIM card. The results are not guaranteed (TextSpy is SIM network dependent, as some store more than others), but in theory if you've lost a message telling you where to meet your mates you can dredge it up from SIM heaven and be only fashionably late.
Of course the only actual use for this combination software and USB SIM reader that I can see is to fuel the flames of suspicion in relationships. Who else would spend £99.99 to find a lost text? Although it seems Gameshow Marathon could have done with one of these.
Related posts: CofE Text Messaging Service