Warrants exist to provide some sort of accoutability. Without any oversight any power will abused. In the US systems of accountability where they exist have become a rubber stamp process. Now any sociopath in a position of power can exercise his need for personal vendetta or nothing at all to smear or harass anybody he likes.
No, the police should not be able to wire tap cell phones without a warrant, because there is always time to get a warrant. Warrants can be written broadly enough to cover upcoming phone calls, or whatever else law enforcement needs. Taping phones is an intrusion, and law enforcement should have to articulate a good reason.
I think giving police officers the ability to wire tap a cell phone is something that would be dangerous for society. A law enforcement agency should go through all the necessary channels to make sure what they are doing is legal and not something that is infringing on the rights of citizens.
I think it would be unconstitutional for the police to be able to wire tap cell phones without a warrant, if there is enough reasonable suspicion to tap some ones phone then you should be able to go to a judge and get a warrant, if the evidence is so weak where a judge wouldn't even grant you a warrant then I don't believe the people should be able to do it anyway.
There is an important fact about the American justice system that sets it apart from Britain. In America everyone is presume innocent until proven guilty in a ideal situation. The police do not have the right to violate anyone's freedome without evidence, and to change that open's a pandora's box of civil liberty issues.
I do not believe the police should be able to wire tap cell phones without a warrant. Laws guarantee a certain amount of privacy to people and authorities are suppose to obtain proper authorization to access cell phones or use them against people. We shouldn't change this, especially with the NSA grabbing up all of our information.