SMS Without a line?

I have seen that asterisk has the ability to send an SMS. All of the examples I have found for setting this up relate to a PSTN, ISDN or
PRI being installed within the system. Is there anyway of doing this via a SIP or IAX Trunk?

not that I know of. There are however a few SMS providers that give you an application for * that will directly integrate * into their SMS gateway… As I recall FastSMS is one of those… not sure tho

it maybe also be possible to do an email => sms, depending on the wireless provider. for example, verizonwireless cellphones can have a text message sent to them by emailing, where ‘xxxx’ is the 10-digit number.