In general, the recommendations that are given by DRS would be applied on the basis of the Automation level set for the DRS cluster. In case of "Manual" the administrator would be manually required to apply the recommendations on his/her discretion. For "Partial automated" the DRS will automatically place the VM on a host based on the resources available at the time when the VM is powered on. For the running VMs it will recommend and the administrator would have to manually decide on the action to be taken for the recommendations. Finally for the "Fully automated" mode DRS would take all the migration decisions based on the Migration threshold set by the administrator. Though, I am not sure if the above answered your question. If not, then kindly elaborate a little bit more on the question.
Yes, the DRS recommendations are published through the VI API. So you can track them using your custom application using the SDK.
For fetching the list you might want to use the Managed Object - "ClusterComputeResource" and then retrieve the property "drsRecommendation"
The current possibilities for viewing the recommendations are either by the VI Client or using the VI-SDK (as mentioned above).
