Good news everybody. Now, Pidgin 2.6.0 and above will be able to send SMS messages and it's working in Indonesia also. At first, i thought it will only work in some countries (excluding Indonesia), but in fact, i just tried to send it to my own number (i'm using Telkomsel's Simpati card) and it's working.
I received a text message from 4246002 and i think it's the global carrier. It will have the format nickname: text message.
If you want to send text message via Pidgin, use Buddies > New Instant Message. Enter your buddie's phone number in form of
+<country code><phone number>
For example: +62123456789
Thanks to Sulabh Mahajan who implemented this feature on Pidgin 2.6.
We are looking for more features in Pidgin
PS: i only test it on Telkomsel. You might try to test it on other operators.
Update (8:44 AM): It works on XL and Three (3). Thanks to Regina
Update (8:47 AM): It works on IM3. Thanks to Bobby
Update (8:54 AM): It works on Mobile-8 (Fren). Thanks to my Mom
Update (9:24 AM): It works on Indosat. Thanks to my Feha