I just ordered a bike and this GPS tracker function is installed without any contract or monthly fees. I wonder how they do that, but probably they have a different system.
I would guess you supply the SIM card.
The Vodofone unit has IMHO, several problems I feel, fixed SIM card being the worst, it is also rather large, modern ones can be much smaller than that, and monthly fees......
I feel that its a good idea to find a SIM card with NO monthly fees, but that is a personal decision.
We have them here where I live from Aldi and Lidl, does Aldi or Lidl or even Tesco do SIM cards in the UK, with no monthly rental, only text and call charges.
Remember, no Data is needed, as all the Trackers I have used you "talk to" them with Text messaging, back and forth.
There is also Smart Phone apps that simplify the texting for some folks, but its really not needed, but the Google map feature is good.
Without software, you edit some text messages and save them for future usage if needed.
Some 12 volt car trackers, also allow a relay to drop power say to the fuel pump if needed, so you can "strand" a car thief, exactly where you wish to!! Somewhere where no buses run, no houses, but the police can find him!!
That might be useful to cut battery power to the bike motor, for example.
Such units start on ebay at around 10 UK Pounds upwards.....
But everyone must decide for himself in such matters.
I have added a fairly standard GPS Tracker manual that I have, the Enlish is not perfect, but its still understandable I feel. It might give some folks here a feel for the units and many use the same or similar commands.
Best wishes to all.