Hi Shadabali,
The idea suggested by Mr. Divekar is the simplest method. However, the driver and the cleaner should be individuals with a great degree of integrity. Unfortunately, this may not always be possible. How do you enforce it? With the advent of technology, this is definitely possible, and there are now many vendors offering products to help you. Choose the one that fits your budget and use it wisely.
Sincerely,
ESP think-tank