For all iPhone users who miss SMS delivery notification, here is a simple trick to make it work on your iPhone.
Just enter these special characters before your message and you will get notification as soon as it gets delivered.
Vodafone/Hutch: *N#
Airtel: !
BSNL CellOne Networks: *N#
So for example, if you are on Vodafone, your message should look [...]

Update: Click here for pre-registering your iPhone with Airtel. Click here for pre-registering your iPhone with Vodafone.
Update (July 1, 2008): Confirmed: $599 for a no-contract iPhone 3G
Update (June 29, 2008): Airtel CEO: No subsidy on iPhone in India
Facts about iPhone 3G launch in India:

Will be launched this year

Will be launched both by Airtel & Vodafone
No [...]