"" I haven't gone walking without taking a whistle and a mobile phone with me just in case anything happens..."
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Those two items will certainly frighten off potential rapists/serial killers.../sarc
A mobile phone is a very good item to have. It's a good move to carry it with you at all times. Think about 9/11... United 93 passengers were able to organise resistance after communicating with people on the ground with their mobiles. All around smart item to have.