That idea make sense, but.. we never know which tarification tricks and issues may be used by various operators, so it's easy to get wrong counters.
As an example - I have 4000 minutes per month for calls to operators A,B,C and D, and 500 minutes for calls to operators E,F and G. Or some SMS messages (to some special numbers) are free and will not be counted by provider, but how will the software get the knowledge about all that?

As a choice, try to ask operator whether they have USSD-number for the query of your balance, with details of remaining SMS, MMS, calls and traffic. My operator, for example, does have such USSD-number and if so, you can use USSD-widget to get the output of the query to your desktop, automatically updated.