TopLine Communications is a London based integrated marketing and communications agency offering PR, SEO, Social Media, Video and PPC to B2B businesses in the finance, technology, employment and education sectors.
I have first hand experience of SMS marketing. It seems to work in African markets but I haven't really seen it received well in the UK.
In my opinion you can get the same level of exposure that SMS offers with a strategic social media campaign. It's less offensive and intrusive, which is the general feeling I got from people that received SMS texts from campaigns that I had run.