One of the options when opening a database file is to execute a script. You can therefore create a script that will find records for "today" using the Get (CurrentDate) function. If you haven't set up a script before, let me know, and I'll help you with it.
The Send Mail script step is available in FileMaker Pro 10 for Instant Web Publishing.
I will investigate the IWP email functionality in FMP 10, in trial mode. New to FMP. It took some time to build the solution and do not want to risk any glitches which may occur from morphing to FMP 10.