The EyePhone is Yon's mobile phone, which was manufactured on Teruga Prime. It is made out of Teruganium and as such can perform a variety of tasks. For example, an application on the EyePhone can be used to generate a intangibility field around the holder of the EyePhone, allowing them to fly and pass through objects until the battery life runs out. This can be done by calling "N0CL1P", though you'll probably get attacked by Dr. Hax as a result.
Because Yon spends most of his time away from Teruga Prime, the phone can rarely make calls, as it usually far beyond the range of Teruga Prime's mobile phone networks.