Brown widow spiders are venomous, but they're considered much less dangerous than the black widow. Although brown widow venom is just as toxic, the brown widow spider injects a much smaller amount of it. Also, only the adult female brown widow spiders bite. Immature and male brown widow spiders don't bite at all.
Yeah, I mainly use it when my son and I are hiking and he asks 'The hell is this weird thing?', I remind him I'm no botanist and pull up seek. It's a pretty cool app. Just looked, surprised the reviews are 3.3, never had any problems with it.