.mmp:

Link against: (in your .mmp file)
LIBRARY PlpVariant.lib //For getting IMEI

Header File:

#include <plpvariant.h> //For getting IMEI

Code:

TBuf<20> imei;
//For getting IMEI
#ifndef __WINS__
// This only works on target machine
TPlpVariantMachineId machineid;
PlpVariant::GetMachineIdL(machineid);
imei.Copy(machineid);
#else
// while working on emulator
imei.Copy(_LIT("123450987685263"));
#endif