This is the 13237th most frequent Russian word.
мобильными
The Russian word "мобильными" means "mobile" or "portable" (instrumental plural form).
In this sentence, 'мобильными' is used as an adjective agreeing in case and number with 'телефонами' (phones) to describe the type of phones being used.
Они пользуются мобильными телефонами для связи.
They use mobile phones for communication.
Here, 'мобильными' serves as an adjective agreeing with 'функциями' (features), describing the characteristics of the features offered by the new devices.
На выставке представили новые устройства с мобильными функциями.
At the exhibition, they showcased new devices with mobile features.
In this instance, 'мобильными' modifies 'приложениями' (applications), indicating the type of applications, showing its attributive use.