Well, there are similar concepts out there. I heard about a service in India, which provides online personal assistance. It consists for the most part of secretary-like work, including things scheduling appointments, ordering gifts for family, finding restaurants and making reservations etc. They are available 24/7 with the limitation of being limited to activities that can be done online or by phone.
You may want to look into their marketing strategy and business model. as it may share similarities to yours. Their advantage of course is that they can maintain a relatively low cost.