Using a phone during طواف is permissible when the phone is being used as a tool to aid the worship — such as reading قرآن from a قرآن application, accessing a دعا collection, or using a counter app to track the circuits of طواف. These are modern tools that serve the same purpose as a printed دعا book, which scholars have always permitted during طواف. Reading from a book during طواف was practiced by some of the Salaf.
Sheikh Ibn Uthaymeen, while he did not address smartphones specifically, stated that reading دعائیں from a book during طواف is permissible. By extension, contemporary scholars permit using a phone application for the same purpose. The key is that the phone is being used for worship-related purposes, not for worldly distractions.
However, scholars unanimously discourage non-worship phone use during طواف: taking or making phone calls, sending messages, browsing social media, or taking selfies. These activities distract the حاجی from the remembrance of Allah, which is the primary purpose of طواف. The Permanent Committee has advised حجاج to minimize distractions during the rites and to focus their hearts and minds on worship. If a phone call is genuinely urgent, the حاجی may step aside, as breaks during طواف are permissible, take the call, and then resume their طواف from where they stopped.