Hello,
I am a linux server administrator and a mobile app developer, so depending on your exact requirements, I might be able to match your perfect developer skill set.
I hope that by WHM you mean WebHostManager by Cpanel Inc.
I can create a mobile app and integrate it to WHM of your server or any server via their APIs.
However, is your budget a bit flexible ? $250 will be enough to integrate and implement all core features and functions of WHM but a bit low for all the features and options of WHM, specially any kind of graphs or realtime data (MRTG, network, bandwidth, loads, etc.)
I would be glad to discuss this project in more details with you, reply me back if you would like to discuss on exact requirements on this.
Regards