I received this message several times regarding the hidden cell phone functions, for example, using it to unlock your car when you are locked out, disabling a stolen cell phone, using the phone when there is no network, etc. All of these sound too good to be true! Here' s what Snoops.com has to say:
1. Situation: You have a phone with the keypad locked or you are in a remote place where there is no cell-phone network available
Claim: Dialing 112 connects you to the emergency service.
Fact: In Europe it connects you to local emergency services even when the keypad is locked. However, the 112 number does not have (as is sometimes claimed) special properties that enable callers to use it in areas where all cellular signals are blocked (or otherwise unavailable).
2. Situation: You are locked out of your car and you have an extra remote keyless entry (RKE) at home.
Claim: Get somebody at home on phone, ask him/ her to press the unlock button of the RKE that is at home, hold your phone at a distance of about a foot from the car door, and boom: your door is open!
Fact: Relaying remote entry system signals via telephone might work if the signals were sound-based, but they're not. An RKE system transmits an encrypted data stream to a receiver inside the automobile via an RF (radio frequency) signal, a signal that can't be effectively relayed via cell phone. (In any event, RKE systems and cell phones typically operate on completely different frequencies; the former in the 300 MHz range and the latter in the 800 MHz range.)
"More than a few people have inadvertently fooled themselves into believing the cell phone method of unlocking car doors actually works because they tried it and achieved the desired results — not realizing their cars were still within range of their keyless remote devices, and the signals that unlocked the doors were transmitted the usual way [i.e., through the air], not via cellular phone connections"
3. Situation: Your cell phone is low on battery.
Claim: Type in *3370# and your cell will restart with this reserve and the instrument will show a 50% increase in battery.
Fact: It originates from a misunderstanding of an option available on some brands of cell phone (such as Nokia) for Half Rate Codec, which provides about 30% more talk time on a battery charge at the expense of lower sound quality. However, this option is enabled by pressing the sequence *#4720# — the sequence *3370# actually enables Enhanced Full Rate Codec, which provides better sound quality at the expense of shorter battery life.
4. Situation: Your mobile phone has been stolen.
Claim: Get the 15 digit code (unique to your p hone) by dialing * # 0 6 # A (before you lost your phone, of course). Give that code to the service provider when you lose the phone, and they will block the phone even if the thief changes the SIM card.
Fact: That function only works with some types of cell phones, and the efficacy of reporting the ID number to a cellular service provider to head off unauthorized use of a lost or stolen phone is limited.
5. Situation: You want to get directory information by dialing 411 for free (the service provider charges about $1.00 to $1.75 for it)
Claim: Dial (800) FREE 411 or (800) 373-3411
Fact: Some business outfits such as (800) FREE-411 do provide free directory assistance services to cell phone customers. However, users should note that the service is "free" in the sense that FREE-411 provides directory information to callers at no charge, but cellular service providers may still assess charges related to placing such calls
Source: Urban Legends
PS: I just got this from blogger bulletproof production. The key combinations (different ones) that he mentioned seem to work.