As I assume these are not pasive devices, what frequency band do they operate on and do you have any idea of power output?
I ask because if I know the frequency I can make my own judgement on what will or not mask the signal.
They use the VHF range so work between 30 - 300 MHz, and apparently operate on their own communications network.
Tracker Locate uses VHF, GPS and GSM technology as fall back systems, but I’m not sure if these devices are used on bikes.
Trackers for motorbikes at present use only VHF.
But their is a new product coming out for cars, which incorporates all 3 (VHF, GSM AND GPRS), as not all of the products available at present do.
Their is nothing confirmed as of yet to say this will be available, but time will tell
But would you really like to have your speeds monitored constantly?..
That’s supposed to be GPS right?
Here is a thought for all, I had and still have a tracker on an 09 Bike, got it nicked and back again in 3 hours. OK good so far, here comes the but, the only reason it triggered at the time of theft is because the thieves decided to break the steering lock, setting off the tracker motion sensor before in less than 2 minutes defeating the Honda HISS and driving the bike off.
My advice is trackers are great for getting things back but if you really do not want them to go in the first place ALMAX it to an anchor.
:w00t: 
Firstlight
the thieving b…ds are very clever nower day they will nick a vehicle or bike and park it in a field or similar
for one week to see if its got a tracker on it. so after a week you can kiss it good by sorry
if you live in n4 then park it in your bedroom its possible it wont get stolen good luck:w00t:
I leave my blackberry hidden on mine when its parked somewhere dodgy and can use the gps tracker online to track it covertly, that way if it gets nicked I’ll go find it myself 
Lets put it like this if you get a monitor, 99% of the alerts you will get will identify movements without the key ignition, thus indicating a potential theft, or someone attempting to steal the bike.
If you get a retrieve you will not get the alert, and will need to report the theft to TRACKER.
The price difference is small, but the potential in reducing the chance of loosing your bike is greater.
I work for them so just thought i would give you my input.
There’s at least two company’s doing tracker for Bikes. You could retrace your movements when you got home (on the Acumen one) , or check the garage wasn’t out for a spin on your pride & joy, and Tracker UK. I found Tracker Monitor UK won’t give up easily ringing you, ringing both your hse & mobile, but it’s a recording so it deems you got the message if/when your landline phone goes to Ans Machine.There was a Police (news night or sommit) program about trackers if anyone else has seen it. So I daren’t open another can of worms on the subject. (I hear the axes grind)
As for subscriptions - you could pay for the lifetime of your ownership if you plan to hold on to the bike. Subscriptions get cheaper if your a member of MAG and possibly other organisations.