GPRS Based Data Logger Testing

GPRS Based Data Logger :-
1) In this there will be one device with lots of many channels in it say pressure, humidity, sensors etc...
the information of this device having various channels will get download to server and from server we can see in our browser

2) the next module is that when suppose say that the temp setting is 20 to 50 then if temp gets rise or less than this range a GPRS module will come here it will send sms to mobile number to server and from server it will be sent to that particular cell

3) Now when we login to the application our first page will be divided in 4 parts
     1- Real time monitoring      2- Active alarms 3- Reports  4- graphical representation of the real time

Now can you all help me in writing Use cases and test cases and different scenarios for this application
 
Thanks,
Punam
pu_musale@yahoo.co.in