I have just read some of the reviews posted on here about the Apps that are around on the market for free. I am constantly on my new Ipod touch and have downloaded the DB navigator, and Cross Country Train Time app.
Both apps are very good time tables, although the times on the XC Train Time app was correct compared to the DB navigator which was two minuets out (on a Knebworth to Peterborough 0938 service)
Both apps offer live map timings and show approximately where the trains are. I can't see the feature of any use on the XC app, as every time I checked to see where the trains from London are, it produces a message saying that the train has left London and that it can't be tracked anymore. On the other hand the DB app shows where the train is against where the next stop is. It does provide a wide variety of station spacing, making it difficult to give a accurate calculation of where the train is, but from what I see it is better than the XC app.
Both apps offer a "Find a Train" feature which are very easy to use. The DB app does however class 15 years as an adult, giving an inaccurate price for child tickets, where as the XC app meets the need for 15 years olds being children.
They also both offer a "Purchase a Ticket" feature. Unfortunately on a Knebworth to Peterborough ticket DB refused to sell the ticket, I'm guessing it is due to it being a German company. However they do offer a ticket reminder which programs a travel reminder on the Ipod calendar for the date of your travels. The XC app does allow a purchase of tickets through a debt/credit card transaction, but does not include a calender reminder!
These are free apps and you have to remember that if you want a tip top working app it will cost. I am also having trouble with National Rail Enquiries and think this is a good alternative to the mobile based website that they provide!
Thats all for now!

please feel free to correct any information I have posted!