The recent launch of Logpost motivated me to build my own API-driven only app. That and my shiney new iPhone 3GS is just craving for me to build some apps for it. So here we go. You'll need a Blinksale account to try it out - but that is the entire point after all.
Please let me know if you have any comments or suggestions.
I actually forgot the URL, but here you go:
For the security conscious: Invoicie doesn't store anyone's password. They are only used to access the API for your current session and are actually sent (securely over SSL) with every request. When you aren't using Invoicie it has no idea what your password or account is.