Hi Kirrily,
From a practical standpoint a weight measurement will only be accurate to 100g and any weekly calculation will not return an accurate weight gain to compare with the standard. It is possible for either digital or hanging scales to return an incorrect result.
E.g. The minimum weight gain expected of say a 5kg child would be 175g per week - or approximately the same as a glass of water. If the child had gained say 160g, that might be recorded as a 0.1kg increase with hanging scales or a 0.2kg increase with digital scales. One would trigger a home visit and one would not. Other questions arise, was the measuring technique good? Was the child dehydrated?
For identifying the need for referral or home visit, it is (IMO) the trend that is more important, as captured in weight based action protocols (e.g. static weight for 3 or 5 weeks, weight loss for 2 or 3 weeks) and only requires that staff review the weights of previous weeks on the OTP card.
Static weight or weight loss in absolute terms should be assessed in accordance with other factors at each weekly visit (e.g. reported appetite, appetite test, episodes of illness - especially involving fluid losses) to determine the appropriate action, which may be medical rather than social / educational.
Staff could also look at the trend in MUAC changes to compare with weight changes. They should change in the same direction, but MUAC will be less sensitive to fluid losses than weight.
I'm all in favour of technology that make the job of staff easier or that improves the quality of care but they can also come with issues around their deployment. There are some interesting experiences from WVI;
https://www.wvi.org/nutrition/mhealth-CMAM-app
https://www.wvi.org/nutrition/video/mnutrition-growth-monitoring-indonesia
Cheers
Paul