When you look for a mobile phone, the choice is overwhelming. When you run your own business, you should consider which one to get. And with this much choice, you really need to look well.
First of all, if you don't just use your phone to make calls, but you also need to read your email wherever you are, you will definitively need a Blackberry. Why ? Blackberry is the only one that will keep you up to date wherever you are, as your emails are pushed towards the device, rather than pulled from your server. But in some industries, you are required or expected to be reachable by phone a lot, but there's not much need for email unless you're at your desk.
Do you see why I said you should consider well ? If you don't need the email service, you might be fine with a more or less regular phone with a good battery so you don't have to recharge constantly. A friend of mine who is a shop owner has the simplest phone he gets for free every year when he renews his contract. No camera, no internet, just gsm and sms - and for his business it's more than enough.
Decide wisely !

Related link : WebWorkerDaily