I would suggest that there are two things that challenge most supervision relationships in their embryonic stages. One is developing a relationship between the new doctoral student and their supervisor that is sustainable for a minimum of three years and the other is dealing with the questions that are important to the doctoral candidates but which occur outside of scheduled supervision session and can delay a candidates progress until a satisfactory answer is available. Lee Yarwood-Ross has eloquently explained one way to address these challenges is via SMS supervision.
As a supervisor I think this is a great idea - the well documented phenomenon of cyber-space disinhibition means that a strong working relationship can be developed even before the first off line face to face meeting which can only expedite the progress of the doctoral student. Thinking back to my first meeting with my own PhD supervisor, I was so intimidated that it was difficult to get the boundaries of my own research articulated. This set the scene for all our subsequent encounters which did not make for a happy experience!
In addition, the middle of the night questions that come to all doctoral students can be dealt with in a timely fashion (although hopefully NOT in the middle of the night!). Sometimes it can be something really simple such as what literature databases to start a search on or the difference between a research aim and a research objective. A simple SMS can help enormously.
The only problem that I can see with this is that some (possibly most??) supervisors may be reluctant to hand their mobile phone number over to students. However, and I've made this point before, doctoral study should be a collaboration between peers rather than a pedagogic student/teacher relationship and should be open to negotiation. A clear discussion of boundaries and ground rules to support satisfactory SMS supervision that is agreed between supervisor and supervisee can add another helpful dimension to the relationship and facilitate the PhD journey.