Can I update PlayerPrefs when iOS app triggers a memory warning

I would like to be able to check at the time when I’m about to load a level if the app has received a memory warning; is that doable?

You have to modify the file to get a message. Check here for an explanation:

Here’s my C# code:

using UnityEngine;
using System.Collections;

public class LowMemoryManager : MonoBehaviour
	//Function is called when a lowMemoryWarning is received
	public void ReceivedMemoryWarning(string message)
		Debug.Log("Low Memory Manager RECEIVED LOW MEMORY WARNING!");

You don’t have to modify anymore. See the last answer here: Is there a way to tell in Unity iOS when onDidReceiveMemoryWarning is received? - Questions & Answers - Unity Discussions

 #import "UnityAppController.h"
 @interface MyOwnAppController : UnityAppController {}
 @implementation MyOwnAppController
 - (void)applicationDidReceiveMemoryWarning:(UIApplication*)application {
     printf_console("WARNING MY OWN APP CONTROLLER -> applicationDidReceiveMemoryWarning()