I'm looking to develop a solution that can send and recieve SMS messages. The recieved messages will then be parsed and stored in a SQL database [Sign Up/Opt In] (free for user), or retrieve content from a database and send that content back to the sender (user pays for content via cellphone credit), And finally the last function will send a message to all users who meet certain criteria in the SQL database.

I also wish to have a three or four digit shortcode that works on both the Vodafone and Telecom networks.

What are my options of doing this, so far I have only been able to figure that

-  I could interface a GSM modem/cellphone to send and recieve sms messages, and parse the data in a script. However,  It seems that interfacing with a datamodem etc doesn't work or won't work on the telecom network (Eg CDMA datamodem that sends sms), and also means I can't have a shortcode (I'm not completly sure)
- I could use a third-party gateway like clickatell, who support two way SMS. This seems like a good option but again it looks like it doesn't support NZ shortcodes?
- Direct connection to the SMSC's of both the Telecom and Vodafone networks (using SNPP/XML etc (whatever the SMSC's protocols are)) -- This seems REALLY expensive, but eventually i'm assuming will be the way to go.

Is there any more options? Using a NZ third-party gateway? Also does any one know a rough pricing on the last option for both networks?

Cheers,

Steve