When I tried David last year when buying mine, he passed me onto Ms Bing at Fangscoo alarm co, as I only wanted a single unit. He assured me these were the genuine article and I had the newer TK102-2 model which does have some additional features over my older TK102 - inc alert for battery charging (or not) in the text message.
Standard delivery was by courier at $30 ! but they agreed to send by Hong Kong Post, tracked at $15. With HKP customs duty seems generally to be avoided unlike DHL or Fed Ex where it is automatic and they do like to add a nice handling fee
I ordered it with the hard wire charger but found that this blows if you leave it connected whilst charging the boat battery thus you need to disconnect it when charging and obviously the inbuilt battery will drain after 48 hrs or so. Once it does, you have to reset the on button/take the battery out/in when reconnecting to the power supply to reconnect to the network
I use a CTEK charger mounted in the console, permanently connected to the battery, and connect to the mains whenever I am not using the RIB. I replaced the hard wire unit with a standard cigar lighter phone charger ( changing the mini USB to the one from the Xenun charger as it isnt mini or micro usb ?) and now have no problems > I presume the phone charger has some voltage/surge protection circuitry ?)
Like Leapy says,
1. The Xenun tracker in NOT waterproof. : I put mine in a normal small IP67 eclosure with the charger and unit
2. you'll need to make sure the tracker is securely mounted and that the usb is taped or similar in place or, at least, check it's still connected after you've been wave jumping : I packed the internal battery tight against the contacts and the back panel, as well as taping the usb connection.
All in all, a great piece of kit > I find that the 'speed' alert is more reliable than 'move' which can sometimes give false alarms with satellite lock or variance.
With speed set at 20 ( kph) once I tow off the drive or from the last set point, the alert is almost instantaneous. With move, it can be up to a mile before it alerts.
Anyway, Ms Bing's e mail is here ; firstname.lastname@example.org
and their website is quite informative
Good luck with the RIBNet bulk buy >> I still remember poor Knot end's valiant attempts
Oh - I use a Vodafone PAYGO sim and its fine. On line top ups and I have not had any issues with not making any voicecalls.