According to the manufacturer, the battery life of the MT42X is up to seven days, but in practice it is more like 3-4 days with normal use. For the MT46X, it is reported that the battery only lasts about one day, which is significantly shorter. There is no precise information on the battery life of the MT40X, but it is an older model with presumably similar or shorter battery life.

Newer models such as the MT42X offer improved functions such as 4G connectivity, GPS tracking and a more user-friendly app without hidden annual subscriptions. The MT46X has GPS and voice capabilities, but apparently has a shorter battery life and fewer additional features than the MT42X. The MT40X is the oldest model and has fewer modern features.

A plan is not mandatory; a prepaid SIM card with a mobile phone contract is sufficient to use the watch for calls, messages and GPS. The app and the watch work with a SIM card without the need for an additional subscription.

The watch is suitable for calls and messages at home via WLAN. GPS requires data, especially when live tracking is activated, which puts a greater strain on the battery. The amount of data depends on the use of the localisation function, with occasional use the amount of data is moderate.

Summary:
- MT42X: up to 7 days battery (realistically 3-4 days), 4G, GPS, no plan required, child-friendly app
- MT46X: GPS, voice function, battery approx. 1 day, fewer features than MT42X
- MT40X: older model, fewer features, exact battery life unknown
- Prepaid SIM is sufficient, plan not absolutely necessary
- GPS consumes data, WLAN can be used at home for calls and messages

This information is based on user reports and tests of the models.