A few corrections & comments
Alert as several people have missed important facts
First, it isn't £15 a month extra monthly bill. It never was.
It is free, thrown in as a bundle with a lot of new contracts. Or you can pay £160 up-front, or you can pay £120 spread over a 12 or 24 month contract eg £5/month. (I know... its usually "discount for cash" not a premium but there you go).
Or if you are a high-value customer you get one for free just for asking. Go on... see how much they love you.
The box can't travel or be used for cheap roaming. They have to track the location, not least because you could take it on holiday to a place Voda doesn't have license & isn't allowed to transmit (eg USA on different frequency).
There are some weird regulatory issues which why data traffic can't just go direct from your router to the Internet but must go via their core: lawful intercept, RIPA or the way the cellular carriers try to block teens from accessing porn. Legally they are the 3G service provider to your smartphone so they have to be able to monitor the traffic. Dumb maybe ("what about WiFi then...?"), but blame lawyers/politicians rather than Voda.
Finally, people who complain about the cost or having to pay for it.... So don't buy one. Very easy.
I object to paying £££ to Sky so I get the privilege to watch programs with ads in that other people paid for. So I don't pay for Sky.
At least Voda offer the choice: would you prefer they charged every subscriber extra tax to build a network to deliver service to the people who can't get coverage...??