Does the Carcomm cradle fulfil my obligations under state laws that require a “commercially designed holder fixed to the vehicle”?

Yes (and it keeps your phone charged as a bonus).

What actually are the laws and penalties in Australia?

Here is a summary [not definitive or guaranteed, as penalties often change] of the current laws and penalties for mobile use while driving. Most are based on the Australian Road Rules as incorporated by the Road Transport (Safety and Traffic Management) Regulation 2000 and Road Transport (Safety and Traffic Management) Australian Road Rules Incorporation 2010 (No 1). This says in paragraph 300:

Use of mobile phones
The driver of a vehicle (except an emergency vehicle or police vehicle) must not use a mobile phone that the driver is holding in his or her hand while the vehicle is moving, or is stationary but not parked, unless the driver is exempt from this rule under another law of this jurisdiction......Use, in relation to a mobile phone, includes the following:
(a) holding the phone to, or near, the ear (whether or not engaged in a phone call);
(b) writing, sending or reading a text message on the phone;
(c) turning the phone on or off;
(d) operating any other function of the phone.


Specific state and territory rules and penalties:

ACT
A driver may use a mobile provided the phone:
- is secured in a commercially designed holder fixed to the vehicle, or
- can be operated by the driver without touching any part of the phone.
Penalty for non-compliance: Fine of
$337 and 3 licence demerit points
NSW
A driver in a moving or stationary vehicle (unless parked) MUST NOT HOLD a phone in his or her hand - whether on or off - other than to pass the phone to a passenger.
Fine of
$304 and 3 demerit points ($405 and 4 demerit points if in school zone)
NT
Fine of
$60 and 3 demerit points
QLD
Fine of
$330 and 3 demerit points - maximum fine of $1500 if contested in court
SA
Fine of
$300 and 3 demerit points
TAS
Fine of
$300 and 3 demerit points
VIC
Using a mobile phone while driving is prohibited, except to make or receive a phone call or to use its audio/music functions provided the phone:
- is secured in a commercially designed holder fixed to the vehicle, or
- can be operated by the driver without touching any part of the phone, and is not resting on any part of the driver's body.
Penalty for non-compliance:
Fine of $433 and 4 demerit points
WA
Fine of
$250 and 3 demerit points