Simple focused-button animator

ScaleOnFocus.cs

using UnityEngine;
using UnityEngine.EventSystems;

// @kurtdekker
// cheap and cheerful "increase the size of the focused button"

public class ScaleOnFocus : MonoBehaviour
{
	[Header( "Percent increase +10%, etc.")]
	public float PercentIncrease = 10;

	[Header("How quickly it changes")]
	public float Snappiness = 1.0f;

	float currentScale;
	float desiredScale;

	private void Start()
	{
		currentScale = transform.localScale.x;
	}
	private void Update()
	{
		desiredScale = 1.0f;
		
		if (EventSystem.current)
		{
			if (EventSystem.current.currentSelectedGameObject == gameObject)
			{
				desiredScale = 1.0f + PercentIncrease / 100.0f;
			}
		}

		currentScale = Mathf.MoveTowards(currentScale, desiredScale, Snappiness * Time.deltaTime);

		transform.localScale = Vector3.one * currentScale;
	}
}

To see it in action, make a UI with a handful of buttons and navigation set up between them.

Drop this script onto each one of the buttons.

Press play and go interact with your buttons.

Yay simplicity!