MBO Toolkit installer comes along with SMP Mobile SDK zip file. Again, its an optional.
If you have any existing MBO based app (built on SUP 2.x or SMP 2.3) and you want to have it on SMP 3.0 by extending then you can select it. Otherwise no need.
Please note, SAP is not recommending any MBO based development on SMP 3.0, this MBO toolkit is just for supporting existing apps.
Also, to run MBO based apps on SMP 3.0, you will need MBO runtime (that comes along with SMP 3.0 runtime/server)
Hope it helps.
Regards,
JK