I (like many other people) have become very reliant upon my Smartphone. Luckily the market is quite competitive both for phones and for service providers so that in general you can get very good value when either buying a new phone or when subscribing to a mobile data service to allow you get the most out of it.
One big exception to this is when you leave your home country. The roaming data rates charged by most operators when you bring your Smartphone abroad are nothing short of outrageous. For example, my provider charges €10 per MByte for data access when I am outside of Ireland so naturally I turn of 3G on my phone and try to survive without connectivity when I am travelling.
In recent years the European Union has done a great service to the public by putting pressure on the carriers to reduce their roaming charges for phone calls within the EU. They have recently turned their attention to also reducing data roaming charges, but this initiative is likely to take some time to bear fruit.
TEP Wireless service which seems like a really cool idea whereby you can rent a pocket wifi from them for the country that you are travelling to. Then you can configure your Smartphone to use this wifi service and you are able to use your Smartphone abroad as much as you want without having to worry about running up large bills. The rates seem quite reasonable, presumably because they buy the devices and sign up for contracts in the country you are visiting so they are paying local rates rather than visitor rates.
I can't wait to try out this service (it was only launched a few weeks ago). Unfortunately they don't offer service in South Africa yet, so I won't be able to use it on my upcoming vacation, but I definitely will try it out soon.