The mobile phone tracker is a SIM card device based on GPRS and SIM compatible communications software. This card is a large capacity (8GB) SIM chip, equipped with a fast decoder program working on data directly in its memory space. When this card is inserted into a cellphone, 5-8 minutes after inputting the tracked one's phone number, it can decode their contacts' pass codes and PIN codes, automatically saving them in the phone. All conversations and SMS can be intercepted, listened to or recorded. The advantages of this device is to make full use of mobile phones, adding a needed function, whilst remaining easy to carry and being safe to use.