My Mini has a 500MB/month Telstra SIM card in it. I need to keep a close eye on my cellular usage with this SIM, as it is part of my Telstra Home Bundle and they will charge me excess data if I go over the 500MB limit - something I worry that I could easily do when I am out and about working, and using cellular data on that iPad.
I love the fact that DataMan shows me the percent usage on the App's 'badge' on the Home Screen - so I don't even have to open it to see where I am up to with my usage. And it will pop up with warnings when I reach certain % limits - which I can define.
So if you are concerned about tracking your up-to-the-minute data usage, check out this app.
There is a version for iPad, which is $6.29, and a cheaper version for iPhone and iPad that is $2.49. This cheaper version doesn't allow you to put the 'badge' on the app to show your current % usage, but is still very handy.
I am very glad that I just installed the cheaper verion on my iPhone, as I discovered that my phone's cellular usage is a little out of control for the month! I accidentally had my Personal Hotspot turned on when I connected my iPhone to my Mac computer, which caused my Mac to 'tether' itself to my phone (thereby overriding the usual WiFi connection). The work I was then doing with Dropbox (and some big files) was then using my cellular instead of WiFi. OW!
DataMan also shows the WiFi data usage by your device on a day-by-day basis during your billing cycle - something that I need on each person's iPad and iPhone in this household at the moment, as we are tracking very close to our monthly 500GB limit this month!!!