Best way to connect Arduino pin (output) to Nokia keypad

What is the best way to connect Arduino digital pin to old Nokia phone (eg. N3310) keypad?

Alternatives: 1. Connect directly 2. Connect through opto-isolator 3. Connect via relay

Option 3 is definitely possible, but I am interested to hear if anyone has successfully done it using option 1 (my preferenced option) or option 2.

Thanks and regards

Option 4: via Bluetooth?