Simmons was caught twice at the Wankhede Stadium, on 18 and 50, but both times the bowlers had overstepped for no-balls and he made the hosts pay dearly for their mistakes as West Indies set up a final against England on Sunday.
Earlier, Virat Kohli continued his rich vein of form by smashing an undefeated 89 to guide India to 192 for two after they were put in to bat.
West Indies lost Chris Gayle and Marlon Samuels early in their reply but opener Johnson Charles kept them in the hunt with a 36-ball 52 and a third-wicket stand of 97 with Simmons.
The right-handed Simmons plays for Mumbai in the Indian Premier League and was only called into the squad two days ago as a replacement for the injured Andre Fletcher.
He cracked seven fours and five sixes in 51 balls and added an unbeaten 80 with Andre Russell for the fourth wicket to take West Indies home with two balls to spare.
Russell, known for his powerful hitting, contributed 43 off 20 deliveries.
Earlier, the West Indian bowlers began strongly, allowing the home team just six runs in the first couple of overs but India then took control in front of a stadium filled to the brim with fans wearing the team’s blue jersey.
India, the inaugural champions in 2007, dropped under-performing opener Shikhar Dhawan and the move paid off as Rohit Sharma (43) and Ajinkya Rahane (40) put on 62 for the first wicket.
That laid the perfect foundation for Kohli, who led his side into the last four with 82 not out against Australia in the previous match, as he compiled a third unbeaten half-century in the tournament.
Kohli began nervously, twice going close to being run out, but made the opposition pay for failing to take their chances.
He struck 11 fours and a six in his 47-ball knock, putting on 66 for the second wicket with Rahane and an unbroken 64 for the third with captain Mahendra Singh Dhoni (15 not out).
India captain MS Dhoni blamed dew, which he said affected spin bowling, and two no-balls for his team’s seven-wicket loss.
“When they started batting the first few overs were fine, but after that there was a considerable amount of dew which meant the spinner couldn’t bowl how they would have liked to,” Dhoni said.
Simmons’ blistering unbeaten 82 off 51 balls was well supported by Charles’ 52 off 36 deliveries before Andre Russell smashed 43 off just 20 balls to help guide West Indies to 3-196.
Virat Kohli’s unbeaten 92 was the No.3 batsman’s third unbeaten half century in the tournament after his 55 against arch-rival Pakistan and 82 not out against Australia.
India had its moments to come back into the match which ultimately ended up in a one-sided victory for the 2012 champion West Indies.
Twice India got rid of Simmons, first when the right-hander was on 18 and then when he reached 50, only to see the bowlers overstepping the crease and bowling no-balls.
“The only thing I’m disappointed about is the two no-balls,” Dhoni said.
“I feel that the point at which the no-balls were bowled were quite crucial. If we had got those wickets, we would have got the opportunity to bowl at one or two overs of the spinners and get away with them without giving too many runs.
“A no-ball is something that can be avoided especially the front foot no-ball … the only thing is that if you don’t want to bowl a no-ball you should never bowl a no-ball.”
Dhoni, who led India to victory in the inaugural 2007 World Twenty20 in South Africa, said he had no plans to quit the shortest format.
“I was hoping it was an Indian media guy because I can’t really say if you have a brother or a son who can play for India as a keeper,” Dhoni replied to a question by a non-Indian journalist.
“Do you think I can survive until the 2019 World Cup?” Dhoni questioned the same journalist, who said: “Yes, sure.”
“Then you have answered the question,” Dhoni said.
The result capped a big day for the West Indies, whose women’s team also shocked tournament favourites New Zealand to book their spot in Sunday’s women’s World Twenty20 final and face four-time winners Australia.
Skipper Stefanie Taylor led from the front for her side, taking three wickets and scoring 25 as the Windies defended a score of 6-143 as the White Ferns finished at 8-137 in Mumbai.
The Kiwis entered the match unbeaten after the group stages and looked well course for victory after Sara McGlashan (38) and Amy Satterthwaite (24) put on 59 for the fourth wicket.
However, the pair fell in successive balls from Taylor in the 17th over and New Zealand’s lower order were unable to guide their team to victory.
West Indies opener Britney Cooper smashed a superb 61 off 48 balls after New Zealand skipper Suzie Bates won the toss and elected to field.
The tall Cooper smashed five fours and two sixes both off consecutive deliveries from Leigh Kasperek to lend momentum to the West Indies innings.
Cooper and Taylor put on 60 for the second wicket after opener Hayley Matthews had fallen for 16 in the third over.
The West Indies were sailing at 1-78 but the dismissal of Taylor in the 12th over triggered a meltdown that saw New Zealand concede just 65 runs and claim five wickets in the final eight overs.
Seamer Sophie Devine starred in the collapse with 4-22 runs, with Morna Nielsen taking 1-14.
New Zealand raced to 1-43 in reply before losing key batters Bates (12) and Devine (22), in the seventh over.
Taylor was unable to conceal her delight at reaching the final.
“We’ve been waiting for this for a long time and it really feels great to have made the final,” she said.
“I do think we can win it if we are consistent enough. We can definitely pull it off.”
Bates said her team was simply beaten by the better side on the day.
“Credit to the West Indies for the way they came out hitting with the bat and Cooper’s innings was amazing,” she said.
“It has been an outstanding tournament for us, but we were on the wrong side of a very good performance by the West Indies today.”
-Reuters, AP, AAP
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