Here's one the guys at MobileCrunch aren't likely to come across in a hurry.  HTID (Hardcore Till I Die) puts on massive events playing uk hardcore which is the bastard offspring of the early 90s hardcore that helped kick off the dance scene in the UK and worldwide.  The typical HTID raver is 18 years old and off their head on a cocktail of MDMA, Blue WKD and Ketamine - the ideal target target for SMS marketing.  So in the HTID posting for their next event on Dontstayin HTID have a mad flash advert with a really clever embedded SMS widget - you enter your phone number and your friends phone number and it sends them a text promoting an event.  They can then text you straight back to say "yeah lets go!" or "hardcore sucks im into funky house now!". 

Here's a screenshot:

An SMS widget makes a great addition to a social media marketing campaign - especially when its as simple as this.  As always, its the people on the edge who are pushing the boundaries.