There is no lack of memory-based services out there for the iPhone. Developers have jumped on the opportunity to use the iPhone as a tool to keep you up to date on your appointments and grocery shopping lists.
One app that does this very well is reQall. It still has its bugs and glitches, but it is a strong effort at what it seeks to do: create a multi-platform system for entering important items that you can later recall. You can enter notes via the web, text, IM, the phone, and of course through reQall itself.
One of reQall's claims to fame is its ability to record a note and the service will transcribe it to text. The key is to talk...very...slowly. If you do, you will have a far greater chance that your note about "the meeting at 2:00" will actually state that in text.
Another great feature is that reQall will "choose" where to put an item: either on your to-do list, shopping list, your notes, or other categories. You can of course to enter notes through the iPhone, web interface, or even through a Firefox extension that gives you the ability to clip and copy text.
You also have control over how reQall notifies you about upcoming appointments. The service can text or e-mail you if you want a reminder. (No word yet if there is a plan for the kind voice of reQall to call you up when you are about to miss your dentist appointment). You can also subscribe to an RSS feed or sync your calendar reminders with any service that uses the iCal standards (like Google Calendar, Apple's iCal or Microsoft Outlook).
Another section of reQall allows you to add a photo note. Say there is a person or object you would rather have a photo of, use your iPhone or Google Picasa library to upload a photo instantly. You can build an online database of important people or items for remembering later.
There are some areas where the service could be better. The search was not strong — some words that I had purposely put in as a note could not be found when searching. The voice recognition has improved from previous versions, but it still jumbled words if they were not spoken with enough clarity. But, if nothing else, reQall has the potential to be an integral aide to a life filled with appointments, meetings, and all sorts of things to remember.