If you are going to be stubborn about not using a mac, but you want an app that will work offline with the iPhone / iPod Touch and Android devices, then I would use HTML 5 to create an offline app.
You can do a lot now with HTML 5 - Google have an email client that uses HTML 5 for the iPhone now and it can work offline etc. If you do this and get the user to add a bookmark to their home screen for your app - it will be almost as good.
If I was you I'd fork out for a mac - or look to see if you could borrow one - or time-share with someone - you will not create a very good quality app without it.
