Please would you tell us what GPS tracker you have.

If you search online for M2M SIMs, you'll likely find some options.

I use a all-network roaming SIM in a tracker, costs around 8p per Mb / per text. Has a UK number. It's only 49p per month for mine but that deal isn't available now, it's now 8p per day rental (with 8p data/text/calls).

I've used Giffgaff before on a tracker too, without a monthly plan their 10p/MB worked out nicely, they didn't round up the tiny amounts of data usage. Their site makes it unclear if it's possible these days to have a SIM without a monthly plan on it.

In reply to a post by Michael_Chare:

Please would you tell us what GPS tracker you have.

Mine is a generic no-name tracker bought from eBay some years ago. This particular model is no longer available but there are plenty listed on eBay. Many of them encourage an ongoing subscription but it's usually possible with a little reverse engineering to identify the particular protocol being used and set it up to work with a system like Traccar.

I've obtained a Tesco SIM to experiment with and put it on the PAYG Lite tariff which ostensibly charges 10p per MB but Ive found it's not suitable for use in a GPS tracker because of the way it (mis-) charges for data.

I've measured the data used by my tracker by monitoring the server (using tcpdump if anyone's interested). It uses 85 bytes of data on each position report and sends reports every 3 mins when static and every 30 seconds when moving. In the worst case, if it were to move continuously for 24 hours, it would use 245 KB in a day. So the maximum usage in a month is 7.3 MB.

If a mobile provider genuinely charges 10p per MB, that would be a maximum of 70p per month.

I activated the Tesco SIM this morning and it's used just over a pound's worth of the initial £5 top-up in around 4 hours. I'm pretty sure that what's happening is that every time the TCP connection drops, Tesco's algorithm rounds up the data used in that connection to a MB. So, less than 100 KB has been charged as if it were more than 10 MB.

I suspect other Telcos do the same but this is the first time I've gathered hard evidence. The advertised price per MB is misleading, at best. Anyway, this rules out Tesco Lite as a contender.

I don't doubt your findings, but running tcpdump on the client side as well if possible and comparing the two might also be helpful - if the thing is retrying ten times before the server responds due to problems between Tesco and your server then you won't see that data but Tesco will be charging for it. It's not going to account for the differences here though, and there's no mention of rounding for data charges in the T&Cs for the PAYG tariff.

It might be worth asking about these plans https://www.thingsmobile.com/business/plans/pay-per-...

Edited by jpm (Mon 17-Mar-25 16:45:35)

In reply to a post by jpm:

running tcpdump on the client side as well if possible and comparing the two might also be helpful - if the thing is retrying ten times before the server responds due to problems between Tesco and your server then you won't see that data

I take your point but the tracker is a black box with a SIM slot and no way of talking to it directly. The only way of measuring its cellular data output is by a man-in-the-middle attack and I don't have the equipment to do that.

I'll do a more controlled experiment by ejecting the SIM for a day to ensure that charging has settled, then put it back for several hours while capturing all the traffic at the server, including any TCP disconnections. If that shows discrepancies in the charging, it may be worth raising the matter with Tesco.

Unforunately, Tesco Mobile doesn't provide any granularity in reporting data use. All I can see is the credit balance decreasing over time.

In reply to a post by jpm:

It might be worth asking about these plans https://www.thingsmobile.com/business/plans/pay-per-...

Thanks for the pointer. If I understand correctly, that would cost just over 2 Euro per month for 7 MB of data.

1p Mobile offer sims for IOT devices and trackers :

https://www.1pmobile.com/not-just-phones

They also offer "Boosts" on their prepaid service , I use the Unlimited 12 month boost @ £48/year:

https://www.1pmobile.com/siminfo?prodid=SBCT500

Thanks. I wasn't aware of 1p Mobile's IOT offer and ther itemised data use is particularly attractive.

£4 per month isn't too bad but I'm still hoping for a service around £2/month. I know that £4/month is a fairly trivial cost in the grand scheme of things but it just seems a waste to pay for umpteen minutes and texts when I need none of them and for a substantial amount of data when I just need less than 10 MB/month. It does show, though, how cheap mobile connectivity has become.

I do appreciate all the suggestions made in this thread. It should give plenty of ideas to anyone else looking for something similar.

try msc's lebara deal; 35gb @75pm for 9 months

Yes, that was suggested earlier in the thread. I'm certainly tempted to give a breathing space while looking around further. I'm not sure it's entirely ethical to take advantage of this offer without the intention to continue after 9 months but, on the other hand, my measly 7 MB/month won't actually cost them much.