ConditionalObserver.cs

using Sirenix.OdinInspector;
using System;
using System.Collections.Generic;

[Serializable]
public class ConditionalObserver<T>
{
    [ShowInInspector]
    public T Value
    {
        get { return _value; }
        set {TestCondtions();_value = value;  }
    }

    private void TestCondtions()
    {
        foreach (var key in condtions.Keys)
        {
            if (key.Invoke(_value))
            {
                condtions[key].Invoke(_value);
            }
        }
    }

    private T _value;

    public Dictionary<Func<T, bool>, Action<T>> condtions;

    public ConditionalObserver()
    {
        condtions = new Dictionary<Func<T, bool>, Action<T>>();
    }

    public ConditionalObserver(Dictionary<Func<T, bool>, Action<T>> condtions)
    {
        this.condtions = condtions;
    }

    public ConditionalObserver(T value, Dictionary<Func<T, bool>, Action<T>> condtions)
    {
        _value = value;
        this.condtions = condtions;
    }
}

Observer.cs

using Sirenix.OdinInspector;
using System;
using System.Collections.Generic;
using UnityEngine.Events;

[Serializable]
public class Observer<T>
{
    [ShowInInspector]
    public T Value
    {
        get { return _value; }
        set {Notify.Invoke(value); _value = value;  }
    }

    private T _value;

    public UnityEvent<T> Notify;

    public Observer(UnityEvent<T> notify)
    {
        Notify = notify;
    }

    public Observer(T value, UnityEvent<T> notify)
    {
        _value = value;
        Notify = notify;
    }
}