Im not sure if its available on iOS or not (but you can normally get the same apps across platforms), but a friend of mine uses one called 'Expense Manager' which he really likes on Android.

There is a good web app; free agent central. Costs money do as it is a full accounts solution.
Expensify looks good
We use xero for accounting, we can do receipts etc through there
What are you using for Accounting?
CHeck out Xero. I would also recommend ronin app for invoicing and there are lots of other tools which are great.