Praise be to Allah.

It should be noted that Allaah has created the universe to worship Him and Him alone. Allaah says (interpretation of the meaning): 

“And I (Allaah) created not the jinn and mankind except that they should worship Me (Alone)”

[al-Dhaariyaat 51:56]

Allaah sent the Messengers to call their people to worship Allaah alone (Tawheed) and to forbid them to associate anything with Him (shirk). Allaah says (interpretation of the meaning): 

“And We did not send any Messenger before you (O Muhammad) but We revealed to him (saying): Laa ilaaha illa Ana [none has the right to be worshipped but I (Allaah)], so worship Me (Alone and none else)”
[al-Anbiya’ 21:25]

Shirk means directing worship to anyone other than Allaah, and du’aa’ comes under the heading of worship which must be devoted to Allaah alone and not directed to anyone else. Hence the Prophet (peace and blessings of Allaah be upon him) said: “Du’aa’ is worship.” Narrated by al-Tirmidhi, 2969; classed as saheeh by al-Albaani in Saheeh al-Tirmidhi. 

Asking for madad from anyone other than Allaah, as mentioned in the question, is a kind of calling upon (or making du’aa’ to) someone other than Allaah, hence it is a kind of shirk. 

It says in Fataawa al-Lajnah al-Daa’imah (2/193): 

The words of some of those who sing nasheed, “Madad ya sayyidina al-Husayn (Help O our master al-Husayn), madad ya Sayyidah Zaynab, madad ya Badawi ya Shaykh al-‘Arab, madad ya Rasool Allaah (O Messenger of Allaah), madad ya awliya’ Allaah (O close friends – or ‘saints’ – of Allaah),” etc, is major shirk which puts the one who says it beyond the pale of Islam (Allaah forbid), because it is calling upon the dead to give them good things, to help them, to ward off danger or relieve them of harm. That is because what is meant by madad is giving, help and support. So it as if the person who says, “Madad ya Sayyid ya Badawi, madad ya Sayyidah Zaynab” etc is saying: Help us and give us of your bounty, and relieve us of hardship and ward off calamity from us. This is major shirk. Allaah says, after explaining to His slaves that He is in control of the universe and that it is subjugated to Him:

“Such is Allaah, your Lord; His is the kingdom. And those, whom you invoke or call upon instead of Him, own not even a Qitmeer (the thin membrane over the date stone).

If you invoke (or call upon) them, they hear not your call; and if (in case) they were to hear, they could not grant it (your request) to you. And on the Day of Resurrection, they will disown your worshipping them. And none can inform you (O Muhammad) like Him Who is the All-Knower (of everything)”
[Faatir 35:13-14 – interpretation of the meaning] 

So He calls their prayers to others shirk. 

And Allaah says (interpretation of the meaning): 

“And who is more astray than one who calls on (invokes) besides Allaah, such as will not answer him till the Day of Resurrection, and who are (even) unaware of their calls (invocations) to them?

And when mankind are gathered (on the Day of Resurrection), they (false deities) will become their enemies and will deny their worshipping”

[al-Ahqaaf 46:6] 

So Allaah tells us that those who are called upon other than Him, the Prophets and the righteous, are unaware of the call of those who call upon them and will never respond to their calls, and they will be their enemies and will deny their worship of them.  

And Allaah says (interpretation of the meaning): 

“Do they attribute as partners to Allaah those who created nothing but they themselves are created?

No help can they give them, nor can they help themselves.

And if you call them to guidance, they follow you not. It is the same for you whether you call them or you keep silent.

Verily, those whom you call upon besides Allaah are slaves like you. So call upon them and let them answer you if you are truthful”

[al-A’raaf 7:191-194] 

“And whoever invokes (or worships), besides Allaah, any other ilaah (god), of whom he has no proof; then his reckoning is only with his Lord. Surely, Al-Kaafiroon (the disbelievers in Allaah and in the Oneness of Allaah, polytheists, pagans, idolaters) will not be successful”

[al-Mu’minoon 23:117]

 So Allaah tells us that whoever calls upon anyone other than Allaah, among the dead etc., will never succeed because of his kufr and his calling upon someone other than Allaah.