that or other summoners can also work like smite or ignite, personally i really like smite.
just think of it this way, smite can give you a 60 seconds or less, combat summoner that either slows and steals their movespeed, which is good vs ganks or if your ally is ganking. Or gives bonus true damage sight if applied (very good vs vayne) and reduces their damage by 20% so its like a mini exhaust which is a strong one for duelling.
then the jungle item gives like a trillion gazillion billion manaregen if you step 2 feet out of lane so that can be helpfull
And killing scuttler provides you with extra vision (and allows you to deny kindred) and is like a free bag of hp regen aswell.
And on the topic of hp regen, throw an ability on a jungle camp and gain 100 health back easy so free pots all the time i guess
And there is more, much more
You get to grab jungle monster buffs, like gromps poison skin to damage enemies when they poke you or trade which will help you win those trades. Or kruggs heavy hands, more easy scuttle killing will help kill minions too and deal more damage vs tower, more like chunking it really hard.
Smite the raptors to clear wards smite blue buff if you are oom kill wolfes for vision and help contest objectives.
And the best part about this is the amount of versatility this gives no other summoner has dueling power ganking power and a whole pile of buffs to choose from. Also you dont even have to kill the camps for the buff, but every camp only spawns with 1 buff to take so it doesnt give anymore untill it respawns the cool thing about this is that you can deny all these buffs from your opponent by walking into his jungle and smiting his camps.
Ive won many a lane by walking into it with a gromp posion skin buff allowing me to win every trade early on.
Ive also put many junglers behind by smiting their redbuff stealing the heal, and by the time they come to take red they are like shit i smited it why didnt it heal and now they have to back without taking red putting them behind a full minute in time at least compared to our jungle which has quite a large impact one you will see as the game progresses however some junglers are more affected then others some can just take red regardless.
Another thing you can do is outlevel your opponent by grabbing jungle camps and gaining bonus xp.
And finally you can buy one of the jungler items, many of them are discount versions of other items but they are cheaper, and offer a few unique stats. Getting to a full item way before your opponent can and gaining the powerspike of it will allow you to bully your opponent most of the time untill they complete their first item.
Its not always a huge advantage depending on which item you will get but enough to extend your lead.
Ive found that warrior gives the biggest powerspike foilowed by bloodrazor then runic echo and cinderhulk, whilst cinderhulk and bloodrazor scale the best.
Just look at this list of advantages you can grab over your opponent with 1 summoner. That being said sometimes teleport had a larger impact when you could go bot to countergank or when splitpushing.
But with the time increase reliance on your support to deward a bush and put a ward in it for ''stealth'' ganks is even bigger now and its even more important to set plays up so reactionary plays wont work well anymore. If your team can't provide this then teleport becomes kind useless
Ignite is still better for securing early kills and ghost is also a good option if you dont want to be kited.
Exhaust can also be quite a good one it provides cc armor reduction and damage reduction works vs against ganks is good in allins and helps when you get a gank. its also an underused option imho.
being not viable in high elo and 
being shuved into the jungle.
