Let the customer sign entered project times on the mobile device

As a user I would like to have the possibility to let the customer sign off the tracked time slots directly on the mobile device. The customer signature should be saved as a picture which is then transferred to the HR product in the background. As an alternative or as an additional step it would be an asset to have a pdf-Report either including the customer signature or as a blank form to be signed offline by mail to the customer. If no email adress for the customer is availabe it should be possible to enter one on the fly before starting the action.