Meet Nigel Pepper and Robbie Clutton, software engineers working for British Telecom. They and team have built an excellent .NET SDK for mobile development (Conference call, SMS, Etc..). They provide a number of services that you can use in your mobile applications
to help you innovate.
The SDK is an exposure of 6 web services: Sms messaging, Conference calling, Voice calling (2 person telephone call), IM and presence, Profile/information store, and a ‘white label’ authentication service. It is still in beta but are Nigel, Robbie et al are working towards promoting the services and exposure to production.
They have a web site which contains the latest details and is lovingly maintained by Nigel, Robbie et al. Take a look at http://sdk.bt.com/