of course you can, even if you get caught tweeting a score during a match it's not like they take you to jail. tons of people will use phones at ipads on courts so it's impossibile to prevent people from using these devices. what itf and atp people look for is suspicious individuals who are clearly there only to gamble or transmit data and trust me they are not hard to spot.
this, this and this.
there are always cheaters trying to screw the system and provide a service without paying for the goods, so the tournaments are trying to prevent this.