I was thinking earlier 'what would I do without a mobile phone'. Everyone I know has one, and for the most part it's my main method of communicating with family and friends when we aren't together. I rely on it heavily, partly because I've been using one for so long. I don't have many home numbers, something I would have amassed did I not have a mobile. I text a lot, handy when a call isn't appropriate or you're trying to arrange something with a group of people. With free minutes I rarely use my house phone unless it's a premium rate call (abroad or 0870, not chat lines)

Can't say I've used one in a business capacity, but can see how they are nothing short of essential for some people.
So yes, were mobiles to be uninvented tomorrow I'd struggle. It wouldn't be the end of the world, but it would take some getting used to, and I'd have a whole lot of home phone numbers to collect.
I can't say really embraced any other mobile devices as much. I had a pager way back in the day, but it was expensive to contact and no good for 2-way communication. Perhaps handy in an emergency situation where you must be contacted, but that's about it.
Oh, and people who unnecessarily wear a bluetooth headset like it was a fashion accessory need shooting. I'm sure for some people it is useful, but I get the distinct feeling some wear 'em just to look like right ponces.