Is it permissible to raise the index finger when supplicating or saying "Ameen" instead of raising both hands, especially when unable to raise them, such as when supplicating while driving a car?

The Sunnah indicated that the Prophet, peace and blessings be upon him, pointed with his index finger when supplicating on the minbar on Friday, and likewise when supplicating with one finger. This shows that one should point with a single finger when supplicating, because the One being supplicated to is Allah, Glorified and Exalted be He. This is a Sunnah that has been narrated and affirmed by scholars, and it is recommended to point with the right index finger when supplicating both inside and outside of prayer.