Review coming soon

Meanwhile you can check the API documentation for all of them.

Website: http://www.fissionsms.com
API : http://www.fissionsms.com/fission_files/downloads/FissionSMS_HTTP_API.pdf

Website: http://www.smsdimensions.com
API : http://www.smsd360i.com/HTTPSpecificationV1.0.pdf

Website: http://www.clickSMS.info
API : http://www.clicksms.info/pdf/ClickSMS_http_2.2.6.pdf