Desktop widget for multi - platform use

Hi everyone, I need someone to help me create a sophisticated widget that can be downloaded from a website. Our customers will be given the link where they can do this, and they will register their email in order to receive the widget directly. Installation and de-installation should be a very simple process. The widget must be able to work on all platforms windows 7, xp mac etc. It must look cool, and sleak and it must not be a copy of your other works, code must be clean. Admin 1) Needs to know how many people have downloaded the widget. Admin will : Load the pictures and prices whenever a new product becomes available online. What the widget must do: 1) User must be able to set up notification pop ups for certain products that are pre set by them. When the product appears a message box should be highlighted. 2) Connect to the admin website and receive rolling updates as an when a new product arrives, when they click on the product the hyperlink will bring them to the page where the product is held. 3) (chat- not sure if you can do this, but if an agent is online they should be able to chat with the person directly only if they want,) 4) Must not be big and bulky looking, but something sleek and non-intrusive to the desktop. I understand silverlight technology can fulfill some requirements, but i am open to suggestions. The most important thing is, the person who is bidding must have done this sort of a widget before and should be able to show me a sample. Or at least have immense experience in this field. Please send me a personal message with samples, long term prospect of working together.... Good day!