I love having Google calendar on my iPhone.
You can set up reminders that can be sent via pop-up (in your browser), e-mail, or event text message.
I personally like SMS text message reminders on important events becasue it is “push” technology–e-mail reminders are good but most of use do not have it open 24/7 to be alerted instantly.
Setting it up in Google is relatively easy.
You will need to have a Google account.
Once you login to your Google calendar account go to “settings” in the upper right-hand corner, choose “calendar settings,” and then “mobile setup.”
It requires you to verify your number by inserting a verification code (which just takes 3-5 seconds to receive and input).