Link to DOI in title

gistfile1.tex

% The biblatex-sp-unified style is at http://github.com/semprag/biblatex-sp-unified

\usepackage[backend=biber,
        bibstyle=biblatex-sp-unified,
        citestyle=sp-authoryear-comp,
        mincrossrefs=50,
        maxcitenames=3,
        maxbibnames=50,
        doi=false]{biblatex}
\newbibmacro{string+doi+emph}[1]{%
  \iffieldundef{doi}{\mkbibemph{#1}}{\href{http://dx.doi.org/\thefield{doi}}{\mkbibemph{#1}}}}
\newbibmacro{string+doi}[1]{%
  \iffieldundef{doi}{#1}{\href{http://dx.doi.org/\thefield{doi}}{#1}}}

\DeclareFieldFormat*{title}{\usebibmacro{string+doi}{#1}}
\DeclareFieldFormat*[book,collection,thesis,unpublished]{title}{\usebibmacro{string+doi+emph}{#1}}
\DeclareFieldFormat*[book,collection,,thesis,unpublished]{subtitle}{\usebibmacro{string+doi+emph}{#1}}
\DeclareFieldFormat*{booktitle}{\usebibmacro{string+doi+emph}{#1}}
\DeclareFieldFormat*{booksubtitle}{\usebibmacro{string+doi+emph}{#1}}