Unlocked similarly to "Driving Mr. Bellic" except for with Little Jacob.
This ability allows you to purchase guns and have them delivered through your cellphone, same as you can order cabs from Roman, and will be unlocked after you achieve a 75% "Like" level, and will go away if you drop below 40%. Jacob is awake from 1pm to 4am. See "Liberty City (5)" for advice on what activities will help raise his "Like" level the best.
You can check your progress:
Start--> Stats--> General--> Jacob Like
**Can be done after completing story mode**