URL can be invoked from any HTTP client (likes of cURL) and is independent of User Agents. Output of business service can be transformed using XSLT style-sheets.
Following URL is an example for invoking business service through single URL. It is capable of logging into application and execute a business service(did I say workflows as well?).
http://host_name/fins_enu/start.swe?SWEDataOnly=1&SWESetMarkup=XML&SWECmd=ExecuteLogin&SWEUserName=SADMIN&SWEPassword=Password&SWEAC=SWECmd=InvokeMethod&SWEMethod=RunProcess&SWEService=Workflow%20Process%20ManagerThis URL can give following output:
SWEDataOnly : Removes unnecessary navigational information from output
SWESetMarkup : Forces the output format to XML
SWEUserName : Application login user name
SWEPassword : Application password
SWEAC : Secondary command that is executed after login
SWEMethod : Method of business service to invoke
SWEService : Business service name
In this example first command does the login and second command executes method on business service.
SWEAPI can help you to query business components and custom methods in case you are feeling a bit more creative.
See how to invoke Siebel workflow through command line.