We looked at the TomTom iPhone app a while ago and that application has just received an update to bring along a few more functions. But the elephant in the room is how you attach your iPhone to your car to use the application. Of course, the TomTom Car Kit for iPhone.

The Car Kit features a number of elements that make it appealing. First up is TomTom's EasyPort mount, so you just have to offer it up to your windscreen and twist and it is secured. You need to know this is going to stay put, as the last thing you want is to see your iPhone heading into the footwell when you hit the first speed bump. Fortunately, TomTom know what they are doing in this area.

You are then presented with a slidey-swively mount in which your iPhone will be held. This bracket means you can have your phone either in landscape or portrait, with the sliding aspect letting you adjust the position relative to the rest of your car, so you don't have to worry about the angle of the windscreen to the dashboard.

Connecting both pieces is a hinge so you can set the phone at the best angle for viewing.

It still sounds expensive for £99 however. But the TomTom Car Kit for iPhone does bring a little bit extra. It's a Bluetooth device, so you'll need to pair it with your iPhone on first use. Once connected it will act as a handsfree kit with an onboard speaker, as well as giving commands using this speaker, rather than the iPhone's built-in one.

The results are much louder audio commands whilst you are driving, with the added advantage of being able to take calls whilst motoring. Incoming calls break through the TomTom app, although unfortunately they don't appear in landscape if that is how you happen to be using the phone.

There is also a rocker switch which can change the volume, although once your iPhone is mounted, it's tucked around the back and not within safe reach to use whilst driving.

The Car Kit is hiding another secret, which is its own SiRFstar III GPS receiver chipset, so you don't have to rely on the one built-in to the phone. This is designed to boost the performance and help clear up troubles encountered in built-up areas. This it certainly did in our tests, however performance will depend on a number of real world factors as it will with all satnav devices.

We found that it noticeably boosted the GPS reception staying in touch whilst in multi-storey car parks and the like, making it a much more seamless experience, avoiding the "Poor GPS reception" notification.

As the Car Kit contains these elements that need power, you'll have to plug it in to benefit from them. A Mini-USB on the bottom of the cradle arm connects to a 12V power supply in your car, cable provided. This sits next to a 3.5mm audio out jack, so you can connect to a car stereo, if you have a 3.5mm input that is. Unfortunately the Mini-USB only provides power and you can't use it to connect to any other devices, i.e., you can't sync or get access to your music through it.

Once connected you have the added benefit of your iPhone being connected to the power all the time, so you aren't depending on the iPhone's battery to run the show. Whether you are using the TomTom application or not doesn't matter, you still get a decent mount and charge for your phone.