Yes I am planning to develop a WP7 app, at some point from here until December.
My App, was/is Desktop centric. I am migrating it to be web centric. It consist of Sync QuickBooks Desktop US to a WM 6.5 Phone
I added xTuple ( a CRM soft) and Openbravo POS support.
It uses sqlite3 extensively.I am migrating the data to be on the web ( using MySql+Asp.Net+ WCF Services). My old app, was a very fat app for a WM 6.5 device 2.2 M+ in size. 60+ tables.
It was done using MFC+sqlite3. The new GUI potentially could be SilverLight. I am working in porting the database first to C#.
2- The phone will be a tough fight for #3 or #4 spot, I dont see it competing with Iphone 4, or Android 2.2
with BB it can. At least this version, I am impress but I have seen the other ones, specially Android with java very easy to code.
You need database support SqlCE or Sqlite3
..because I am moving to the Web the data, an Azure solution may interest me, but tooo expensive. I have no idea how much it will cost to host this data on the Azure platform.
I am not doing this for financial gain, just for my own intellectual pleasure.