Given the high regard in which both the iPhone and the TomTom satellite navigation system are both held, one might assume that the marriage of the two would be a match made in heaven. Sadly, the reality is somewhat less enticing.

As you might imagine, TomTom for iPhone turns your mobile phone into a fully functional GPS SatNav system, with the ability to plan routes and give audio guidance as you drive.

Using the system is relatively easy; once your location has been noted by the TomTom software you can input a destination and it will give you the best available route. TomTom’s IQ Routes software is probably the best out there, given that it uses real road speeds rather than relying solely on designated speed limits. When it works, it works excellently – the system is able to detect areas that fall foul of heavy traffic and will find alternative roads for faster, less stress-inducing journeys.

Another feature we liked was the ability to use your iPhone’s contact list to create destinations. So if you’re off to visit a friend but are unsure of the exact route, you can link directly to his address in your contacts and TomTom for iPhone will give you a suggested route. It’s slick and intuitive, which is exactly what you’d want from such an application.

Sadly, the wheels come off in spectacular fashion when it comes to other features.

Firstly, TomTom for iPhone is seriously lacking when it comes to customisation and adaptability. For example, if you already have a TomTom account there is no way of linking it with this particularly iteration of the system. Also missing is the ability to get regular updates as you drive; given that the iPhone is an “always online” device, this is rather puzzling.

There are also physical considerations to take into account. Most dedicated SatNav devices come with a dock which allows you to secure them to your car’s dashboard – a feature that the iPhone obviously lacks. A TomTom iPhone car kit has been confirmed, but at £100 it’s not cheap, and bumps the combined cost of the package up to £160.

However, the biggest issue with this app is reliability. We noticed that it’s often hard to get a precise GPS lock, with the program sometimes taking several minutes to properly locate our current position. Also, TomTom for iPhone doesn’t operate as smoothly as a stand-alone SatNav; we can only assume this is down to the fact that the iPhone is performing other tasks in the background which results in a hit for TomTom’s overall performance.

Given the exorbitant asking price it’s difficult to recommend this app. The TomTom name lends it a fair degree of cachet, but the sad fact is that stand-alone SatNav systems are available for the same price as this download and they offer a better experience. While fusing the iPhone with TomTom might free up some space on your cluttered dashboard, you’re likely to return to using a separate system after a few weeks of frustration.