I think you should still consider using paper and getting clients to sign a form to give consent.
Even if it’s just a basic form where you write down the treatment and ask them to sign and date it. You can still keep more detailed records regarding the treatment electronically.
If someone decides to make a claim against you, you need to show that the client consented to the treatment. If the client lies and says you didn’t advise of the risks (e.g. contra-indications), at least you can prove that she signed to agree to the treatment. That demonstrates that you were following professional guidelines and makes it more likely that you carried out the service correctly making her claim more difficult to prove.
Also, if you store client data electronically on a device, consider using a cloud storage system so that if the device becomes corrupted or lost, you still have access to the client information.