Home Secretary Jacqui Smith hailed the pilots as a "huge step forward" in helping parents to protect their children.
Sarah's mother, Sara Payne, welcomed the pilots, but she said they were only a "first step" in a continuing battle.
Under the pilots, parents, carers and guardians will be able to ask the police for information about people directly involved in their own children's lives.
Scenarios could include a single mother who wants to find out about her new boyfriend; parents with concerns about a neighbour who plays with their children; or perhaps even informal sports coaching beyond schools or recognised organisations.
In each of the pilot areas police will be obliged to look into the background of individuals and consider providing information to parents.
This might include confirmation of a previous conviction for sexual offences, domestic violence or an indication that the individual is showing worrying signs of being a danger to children.
Police will run two types of checks on the individual - a priority check within 24 hours and a full risk-assessment within 10 working days.
If the person is found to have convictions for child sex offences, the case will be referred to a multi-agency panel of representatives from the police, probation and prison services, and other agencies.
The panel may choose not to disclose information, such as convictions, if it concludes the individual no longer poses a risk to youngsters.
However, there is a presumption that parents will be told if the person does pose a serious risk.
Parents could face court action if they pass on information about an offender to others in their community, a move designed to prevent vigilantism.
Other people unconnected to a child who ask for information about a potential suspect will not be given information, even if their concerns turn out to warrant action.
Ms Smith: "There are few crimes more damaging, more emotive and more sensitive than sexual offences against children. I want to see every child living their lives free from fear.
"Giving parents the ability to find out if someone close to their child poses a risk will empower them.
"With the help and support of police and other agencies, it will also help them to understand how to better protect their children.
"These pilots, which have been developed in conjunction with leading children's charities and campaigners, are a huge step forward."
Lessons would be learned about the management of sex offenders during the trial, Ms Smith added.
Diana Sutton, head of policy at the NSPCC, said time would tell whether the schemes kept children safer or merely created a "false sense of security".
"We strongly urge people to remain alert to the fact that not all child abusers have criminal records because many are not caught and charged with an offence," she said.
Child protection charity the Lucy Faithfull Foundation said it was concerned publicity around the pilot projects could drive sex offenders underground, and called for careful monitoring of their impact.
And crime reduction charity Nacro chief executive Paul Cavadino agreed the risk of attacks could prove to be counter-productive.
"The real test of these pilots will be whether this information can be kept confidential to the parents or whether it spreads to other people, causing a risk of vigilante attacks."
But Sara Payne welcomed what she called the beginning of the end of "secret-keeping", saying it had been "a long eight years" of campaigning since her daughter's murder.
"Secret-keeping is the biggest tool and weapon [that sex offenders] have against our children," she said.
"This is about taking away the fear that you have as a parent about who they may be playing with. This is about positive parenting: be open about it, get your kids to talk."
West Mercia Chief Constable Paul West, the senior police spokesman on child protection policy, said: "These pilots empower the parent to take the initiative and register an interest in an individual.
"I don't think it will open the floodgates - but I do think that there will be people who will come forward with concerns."
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