Good question. In addition to a budget amount, Azure requires you to specify a threshold value – a percentage of the budget – and triggers an alert only when your consumption hits that value. CloudAlarm, on the other hand, only requires you to specify the budget and notify you if your current consumption is estimated to exceed it.
For instance, suppose you set a budget of $1000 and a threshold value as 50%. Now suppose that someone creates a resource accidentally with a wrong tier – say an expensive SQL database – that has a cost of $50 per day while the need and approval was for a $1 per day tier. You also have other resources costing $30 per day so total cost is now $80 per day.
With Azure budget actual-based alerts, you'll likely get notified on the 8th day by which time you have consumed 50% ($560) of your budget, of which $350 is the cost of that database alone instead of $7. With Azure budget forecast-based alerts, you'll still get notified after a few days again when you've consumed 50% of your budget as per the forecasted cost for the month. We're not privy to the exact algorithm that calculates forecast cost, but in either case the important point is that you need to have consumed a threshold or percentage of your budget amount before you get notified.
For the same scenario of $80 being spent per day, CloudAlarm will alert you on the 2nd day itself by which time you've spent only $50 (instead of $350 as in case of Azure budget alerts) on the wrong tier of SQL database.
CloudAlarm has to wait for a day because Azure doesn't provide a way to know the actual cost for a given resource, until that resource has been consumed for a day. However, with 'New Resource' alarms (not available in Azure) you can even bypass this limitation by setting up alarms to notify you if a resource is created in tiers you don't expect to use. resource alarms are run every few minutes so you'll not even consume few dollars for the same database scenario and you'll get notified of the mistake. You can immediately amend the tier and literally save yourself almost the entire cost – and a charge of $2 or so for an hour would be the cost incurred instead of hundreds of dollars if you had relied on Azure budget alerts.
The forecast alert also requires a threshold amount so essentially you have to consume that threshold before Azure will notify you. Additionally, the consumption calculation will be based on Azure forecasting algorithm, which usually can be way off from the actual consumption as it relies on historical consumption data.
We can consider it if there's a demand for it. Btw, CloudAlarm only requires a read-only access [0] to the Azure subscription, so certainly we can't make any changes to the resources.
CloudAlarm is presently in beta so there's no plan/pricing info available yet. We intend to have a subscription based model with plans to accommodate needs of individuals to businesses and large enterprises/universities.
With Resource alarms, you can track and get alerts based on events related to resources. Presently, we support two events – 'added' and 'deleted' and you can use operators, service tiers, resource groups to further constrain a trigger condition for the alarm. So you can setup "notify me if any new resource is created" or you can be specific - "notify me whenever a new SQL Database of greater than Standard Tier is created"
This isn't only good for cost tracking but also for accidental and risky mistakes like you can track and get alert for accidental deletion of important databases and virtual machines almost instantly.