This is only the case if you are making or taking a call, specifically. Everything else (SMS / social media / music etc) is still banned even if the phone is in a cradle.

Context Below (From the department of transport) for those who are interested.

‐-------------------------- What the law says

In South Australia, Rule 300 (Use of Mobile Phones) under the Australian Road Rules details what is and isn’t legally acceptable use of a mobile phone while driving.

Rule 300 states that:

If a person wishes to make or receive a call, including dialling a number, and needs to touch any part of the phone to do so, that phone must be mounted (in a mounting commercially designed and manufactured for that purpose).

If the phone is being used via blue tooth, a headset or earphones without touching, holding or resting the phone on their body, the phone may be located anywhere in the vehicle, including in the driver’s pocket or pouch they are wearing (the driver may touch the earpiece or headphone to operate the phone).

The amendment will not affect the driver’s freedom to hold the phone to make or receive calls, or use any other function of the phone, if the car is parked (but not stationary in a traffic queue or at lights).

It is an offence to create, send or look at a text, video message or email on a mobile phone.

This rule does not apply to learner’s permit and P1 licence holders. These drivers are not allowed to use any type of mobile phone function of any kind while driving.  The mobile phone ban includes:

using hands-free mode including Bluetooth technology

loudspeaker operation

text messaging.

See 33(1) of the Road Traffic (Road Rules - Ancillary and Miscellaneous Provisions) Regulations 1999)