Malorie Blackman 
Operation Gadgetman! 

Beans calls her dad  »Gadgetman » because of the weird and wonderful gadgets he comes up with – everything from exploding biscuits to Spy Kits. But when Gadgetman accidentally invents a device that could be used to steal millions of pounds, the wrong people find out and Gadgetman is kidnapped!With the help of her friends – and her special Gadgetman Spy Kit – Beans is determined to track down the kidnappers and rescue her dad. But can she find Gadgetman before he is forced to hand over the details of his invention…?