I know that the MBP have the sensors for the HDD but i heard somewhere that some of the macbooks do to. the reason i ask is because i want to get 'iAlertU' and i dont know if i have it... at least i dont think i do
Every MacBook/MBP has motion sensors built-in, and if I'm not mistaken, the last revision of the G4 laptops had sudden motion sensors built-in. So yes, your MacBook does indeed have motion sensors built in.