how does ollydbg memory breakpoint works

all break points that are availbale via gui is available via commandline plugin too bpx ,bp etc including conditinal break point
open the help file for details about various formats
or type help in commandline plugin itself

@dexep
use VirtualQuery() for calling process related page information
or VirtualQueryEx for remote process related page info
it returns a MEMORY_BASIC_INFORMATION struct filled with all those details

typedef struct _MEMORY_BASIC_INFORMATION {  
PVOID BaseAddress;  PVOID AllocationBase;  
DWORD AllocationProtect; 
SIZE_T RegionSize;  
DWORD State;  
DWORD Protect;  
DWORD Type;
} MEMORY_BASIC_INFORMATION, *PMEMORY_BASIC_INFORMATION;

the allocationprotect has the constant that defines the pages protection status

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/memory/base/memory_protection_constants.asp