From what I have determined from my uint (so far),
+SIND: 0 = No Sim Card
+SIND: 1 = Sim inserted
+SIND: 3 = Almost Ready (No SMS support, Yet)
+SIND: 4 = Ready
+SIND: 7 = Pincode Needed
+SIND: 10 = Something to do with the phone book?
+SIND: 11 = Registered with the Mobile network
Hope this helps you a bit..