This nice little mod adds a lot to immersion (for me at least). It makes certain NPC travel between settlements doing "business". They will travel according to set schedule. Mod is configurable and needs to be switch on via In game menu after installation.
It did not cause issues when I used it before. Not checked for error though.
Some more info, as per the mod description:
Lillith Maiden-Loom travels to Riften on the 21th of each month, browses the market if she still has time, then dines in the inn and sleeps at the Bunkhouse. The next day, she will follow Maven around on her daily routine, followed by dinner at the Black-Briar manor. She heads back to Whiterun in the morning of the 23rd.
Ennis travels from Rorikstead to Whiterun to browse the market every morndas, middas and fredas.
Faendal brings wood to Whiterun every tirdas and turdas and spends some time at the Drunken Huntsman afterward.
Commander Caius travels to Riverwood on tirdas, patrols briefly and spends the next eighteen hours at the inn, staying the night. He does the same for Rorikstead on Fredas. Does not take effect if Whiterun is under Stormcloak control.
You can choose to have the Hirelings rotate around the inns of Skyrim on a daily basis. They will return to their original location on the weekends.
Urag Gro-Shub will visit the Frozen Hearth inn on the weekends in the evening. This is useful for certain quests, but his dialogue won't make sense, so you might want to keep this one disabled. I'm also keeping it disabled during the relevant stage of the "Elder Knowledge" quest, because you'd still need to enter the college to collect the books.
Are your NPCs in peril while travelling? Technically, they can't die if you aren't near them, so you can rest assured that Lillith Maiden-Loom will always return safely if you don't accompany her or run into her along the way. But if you do, and you find yourself attacked by werewolves, well, at least it makes the game interesting.