Salesforce: Apex Trigger to Reassign Contacts and Open Opportunities

Standard Salesforce functionality allows for the reassignment of Contacts and open Opportunities when the Account to which these records are associated is reassigned to a new User. Clicking the "[change]" link next to the Account Owner field on the Account detail page will allow you to step through a process by which you select a new Account owner and save the changes. Once the changes are made the system will go out and reassign all Contacts and all open Opportunities owned by the old Account Owner to the new Account Owner. This is useful and so automatic that you may not even be aware that it happens.

So what if you work for an organization where Account reassignment tasks are handled in mass or they are handled by some Salesforce integration? Unless the admin performing the mass updates is explicitly updating the related records or there is code in the integration explicitly reassigning the records, the related Contacts and Opportunities are remaining assigned to the old Account Owner.
That's why I wrote the following trigger. It will perform the ownership update for related Contacts and Opportunities when the Owner of the associated Account is updated.

For some security might be a concern sending the data via URL parameters.
Up to this point, I have not been able to confirm if Google is officially supporting SSL connections to rectify this problem. However the following seems to be fine

trigger reassignRelatedContactsAndOpportunities on Account (after update) {
 try {
  Set accountIds = new Set(); //set for holding the Ids of all Accounts that have been assigned to new Owners
  Map oldOwnerIds = new Map(); //map for holding the old account ownerId
  Map newOwnerIds = new Map(); //map for holding the new account ownerId
  Contact[] contactUpdates = new Contact[0]; //Contact sObject to hold OwnerId updates
  Opportunity[] opportunityUpdates = new Opportunity[0]; //Opportunity sObject to hold OwnerId updates
  
  for (Account a : Trigger.new) { //for all records
   if (a.OwnerId != Trigger.oldMap.get(a.Id).OwnerId) {
    oldOwnerIds.put(a.Id, Trigger.oldMap.get(a.Id).OwnerId); //put the old OwnerId value in a map
    newOwnerIds.put(a.Id, a.OwnerId); //put the new OwnerId value in a map
    accountIds.add(a.Id); //add the Account Id to the set
   }
  }
  
  if (!accountIds.isEmpty()) { //if the accountIds Set is not empty
   for (Account act : [SELECT Id, (SELECT Id, OwnerId FROM Contacts), (SELECT Id, OwnerId FROM Opportunities WHERE IsClosed = False) FROM Account WHERE Id in :accountIds]) { //SOQL to get Contacts and Opportunities for updated Accounts
    String newOwnerId = newOwnerIds.get(act.Id); //get the new OwnerId value for the account
    String oldOwnerId = oldOwnerIds.get(act.Id); //get the old OwnerId value for the account
    for (Contact c : act.Contacts) { //for all contacts
     if (c.OwnerId == oldOwnerId) { //if the contact is assigned to the old account Owner
      Contact updatedContact = new Contact(Id = c.Id, OwnerId = newOwnerId); //create a new Contact sObject
      contactUpdates.add(updatedContact); //add the contact to our List of updates
     }
    }
    for (Opportunity o : act.Opportunities) { //for all opportunities
     if (o.OwnerId == oldOwnerId) { //if the opportunity is assigned to the old account Owner
      Opportunity updatedOpportunity = new Opportunity(Id = o.Id, OwnerId = newOwnerId); //create a new Opportunity sObject
      opportunityUpdates.add(updatedOpportunity); //add the opportunity to our List of updates
     }
    }
   }
   update contactUpdates; //update the Contacts
   update opportunityUpdates; //update the Opportunities
  }
 } catch(Exception e) { //catch errors
  System.Debug('reassignRelatedContactsAndOpportunities failure: '+e.getMessage()); //write error to the debug log
 }
} 

The code itself is fairly straightforward. If your Users/Admins elect to perform one-off Account ownership changes via the Salesforce GUI then the regular functionality still applies. This code simply keeps you covered when performing Account assignment changes in another manner.
-greg