If the equipment survives after you remove the cell phone, there is a very little chance to observe side effects, or property changes. However, if you keep the cell phone near the area where the main power supply or other power circuits are installed, you may blow them, especially if they are not shielded (mostly in new monitors). The effect on other low power circuits is only temporary, it may disrupt their functionality, but after a reset or power cycle, everything should be fine.
/pisoiu