The short answer is that there is no technical requirement. You do not need a Mobile Platform to build a mobile app for an SAP HCM solution. Some partners of SAP have already demonstrated this. This approach works when
- You only build a few apps for a specific device for a small number of employees
- You don't care about remotely managing data in the devices your employees carry
- Your employees are very careful and will never misplace their devices, so security is not a concern
In other words, when you get serious about mobile deployment, you should plan to have a platform such as the one provided by Sybase. I hope this explanation helps.