There are 2 possibilities to debug DolphinV4 platform applications:

Custom UART
Custom debug messages using sprintf, uart_sendBuffer
Pros:
+Real time
+Fully customized

Cons:
-UART blocked
-Custom implementation needed

Keil Simulator
Debugging the application in the simulator
Pros:
+Single stepping
+Breakpoints
+Watch

Cons:
-DolphinHW events not supported (radio, timers, sleep modes)