Yes, Data is maintained locally on the mobile device or tablet. You can work independently and synchronize when you are able to establish a connection.
Yes. You will need to get wireless data service from any wireless data provider. Some providers, like AT&T, Sprint, Verizon sell converged devices that are voice phones with a built-in Windows Mobile.
OIS iMobile is the next generation software (iPad/iPhone/Android) for sales force automation, van sales, store calls, merchandising and in-store audits.