CGMS - Continuous Glucose Monitoring System. There are a few around and different ways to do it. What they all do though is take blood sugar readings approx ever 5 minutes and transmits it to whatever device you are using. They all have a sensor which is inserted by mum or dad (very much like a canula for a pump) and left there for minimum of 6 days. Each one has a transmitter which you then attach to the sensor part that is outside of the skin. The sensor itself is under the skin mixing in with the intistitial fluid. It is the intistitial fluid that is read and not the capillary blood like from the fingers. The capillary blood is more accurate, the intistitial fluid generally has a small time delay.
So systems - there are stand alone system and there are those that are combined with pumps. There are only two at the moment combined with pumps. The original one was by Medtronic and their latest model is the Medtronic VEO pump with CGMS using Enlite sensors. We use this so have first hand knowledge of them. My daughter has used sensors full time for 5 years now. The other pump combination on the market is the Animas VIBE which is the 2020 with updated bits to it plus the combined Dexcom 4th generation sensors. This is unfortunately at the moment licensed for over 18 years but there are some consultants who will give this to younger people off license which is fine. There are pricing differences between the two and you can generally get way more than 6 days use out of one sensor both with the VIBE/Dexcom and the VEO/Enlite. Some have been known to get 21 days usage. The longest we have managed is 14 days. The transmitters for both these send all the readings to the pump so you can see what is happening on the pump screen.
Then there are the stand alone CGMS so they are not combined with the pump so those that have the Roche Accu Chek pumps or indeed those on injections regimes will go for these. There is the Dexcom which is sold by Advanced Theraputics in the UK, instead of a pump (like the VIBE above) you have a hand held piece of kit that the transmitter sends all the readings to. There is the Medtronic Guardian which uses the enlites and you have another hand held device like the Dexcom. There is also the Navigator by Abbott. I don't know much about this one as haven't seen it or used it but it will work the same way as the others pretty much.
They all have alarms. They all can predict when a hypo is going to happy by a certain time depending on what settings you put in. For example I have 4.0 as the hypo setting in ours. I have set it up that according to how her levels are falling that it will alarm 15 minutes before it suspects she will be hypo. So you can ward off that hypo. The same for highs.
With the VEO/Enlites they have an added extra of the Low Glucose suspend. For us this is set at 3.4 mmol. That means when the sensors transmits to the pump that Jessica (my daughter) is 3.4 mmol the pump suspends all insulin delivery. It will alarm like mad but at night if you don't hear it then it will stay suspended for two hours. It will then turn back on all basal rates but if the sensor is still detecting 3.4 and under it will immediately suspend again. However if you hear the alarm as it suspends you just test levels and treat the hypo. More often than not it will be pretty much right with its levels but occasionally the reading may be a bit out.
None of these gadgets are 100% accurate. Some love the Dexcom, some love the Medtronic Enlites. There is no right or wrong, any sensor is better than no sensor. I believe, as do others that the sensor chooses the person, bit like the cannulas for the pumps choose the person. You can trial them all (the stand alone ones), it costs of course (what doesn't) but it is worth trialling them to see which suits your child better.
They are hard to get funding for but worth the fight. It is once more a post code lottery. Some PCT's just won't fund them at all, some willingly give over the cash! To privately fund them it is not cheap but again if you have a bit of spare cash you couldn't put it to much better use than a sensor system.
I hope that has helped, happy to answer any questions and I'm sure I left bits out and there will be loads of others who can answer and help as well.