Long range communication for a wearable device
You have a collection of options:

Mobile phone networks: any of the options, GPRS upto 4G depending on cost your willing to pay and data you need to transfer. Probably the easiest and most reliable, assuming that the mobile networks are available in the operational area. 

Some analogue radio communication. I'm pretty sure that all of the frequencies that will give you the range are license controlled (in Europe, Asia and N America), but it might be worth investigating depending on how much you can work with the countries you plan to operate in. High power consumption, license fees and large antenna are all issues with that.

Satellite phone: lots of low level data communication takes place over satellite phones already, so I'm sure you could add something to that. Advantage is they cover all the world (depending on you provider) as long as you're outside (some work inside, sometimes). Power consumption is high, as is the required equipment cost.

Mesh network: if you have enough of these sensors spread from where you need the data to the furthest node, you could use a mesh network of nodes, one every 20 metres or so, and link one to another to get to the data centre. Clearly this is lots of nodes, lots of cost, and each node needs it's own power supply.

No doubt there are other methods, but looking at miles, you are best to use existing networks; mobile phones or satellite phones.