Prior to selecting a camera system, it would be wise to take a step back and analyze the entire situation. People who work unsupervised in customers' homes face a serious risk of harm from false accusations, and I don't doubt that your desire to protect yourself is sincere. That being said, there are several important issues to consider.
I do not know where you work, but many states have laws against filming someone without their consent (especially in their own home). Your employer may also take issue with you privately recording customers, and many large employers have policies expressly forbidding such behavior. I would advise you to contact an attorney in your area before taking any steps toward recording customers.
I don't fault you at all for wanting to protect yourself (I assume that almost everyone on this form takes self-protection very seriously). I'm old and married, but I can only imagine how scary it is to date or be alone with coworkers/customers of the opposite sex in an era when any accusation of impropriety can ruin your life before you even have a chance to defend yourself. Still, discretion is the better part of valor and you need to make sure that you are taking the proper legal steps to protect yourself (which is also something forum members tend to take very seriously).