The evolution started...

First of all not so easy to find the right solution and the right company.
Since I'd like to send sms with special accent characters like íéűáúőóü and ÍÉŰÁÚÖÓÜ (I just hope you'll see on screen).

The most important advantage of smsxchange.com the native support of these special characters. The websms from their homepage or from any other server with 2 simple file (1 html + 1 php file) enough to send those special chars.

You can send standard GSM alphabet messages via E-mail to SMS too.

Several methods supported:

Method I: Sending SMS to Single User
Method II: Sending Same Message to Multiple Users
Method III: Sending Same Message to Multiple Users

Some other nice function also available but the list advantage pretty short for me.

Why?

Several times try to reach the support but no answer at all.

They running very good service, several gateway exist for more reliable delivery.

You can send so many msg type: Unicode,Blinking,Flash,Group Graphics,Picture Messages,Logos,Ringtones,Screensavers,Animated Screensavers,Profile Download,Nokia Business Card,Nokia Calender Events,Wap OTA

and here is the not too recent list of compatibility:
Compatibility list

Worldwide coverage:
Coverage and prices

Technical documentation also available on site with example scripts:
Technical documentations