You use shopping lists? The application "I Want to Buy" allow you to put your shopping list in your iPhone. With this app your shopping list will be with you always and anywhere. And you can easy edit it as soon as you want to buy something or you have bought it.
The application can calculate cost of your purchases. So you can estimated how much money you need for your shopping and whether it is worth to spend so much money.
Each purchase can be marked with a category and a shop where you plan to buy it. Then you can group and filter your purchases by categories and shops. So in bookshop you will see books only in your shopping list, but not clothes or food. Furthermore you can use colored markers and goals for grouping and filtering your purchases; meaning of markers and goals you can define on your own.
When you have bought something, the application removes the corresponded record from your shopping list, but keep it in history. With the history you can remember when you bought something and how much it was. With grouping and filtering you can see how much money you have spent on each thing category. In addition you can use records from history as a pattern for your new purchases when you add them to your shopping list. The application keeps records in the history some time (1 month by default) and then removes them automatically.