The annual budget of the Met Police is £3.28b, the programme budget for WHO (programme costs only) is US$4.84b, NYPD $5.9b
A new global organisation, starting from scratch with staff as well as programme costs to cover, would not have transformative effect on a budget of £3.8b
Trackers don't work on people, btw, because of
a) signal strength when passing through skin (v poor - think of how close your pet has to be to the scanner to have microchip read). Tracking wild animals is done through external devices akin to the tags of the sort used on criminals
b) if you want it to transmit, rather than just be read, then it needs a battery, and for any reasonable life, it won't be an injectable because of size and the needs to replace/recharge
I do not think the 'celebrities' who were looking in to this were looking at real, existing, fit for purpose devices. I guess they were speaking for effect, and then using one of the many portable or wearable GPS devices that use real time tracking (eg mobile phones or sport and fitness trackers)
I just read the Wikipedia on Dutroux for a quick reminder of the case and it's timelines. It's shocking.